Not good at organizing parties...

How about an afternoon tea party? Less formal than a dinner party. As it’s in June you might even be able to hold it outside,

Does she even like parties?
I would be very unhappy if any of my friends organised one for me!

You all need to consider very carefully whether she would actually want a party, and if you decide to go ahead then maybe keep it simple. Don't invite all these groups, just keep it small with just her close friends. You only need four couples, some tea, sandwiches and a cake. It will qualify as a party but not be overwhelming.

Does she have children? If so, they might be doing something for her.

Personally, I would hate anyone organising a party for me. If her DH is keen, he ought to be the main man doing it.

When my friend reached 70y she decided against ‘one big party’. Like your friend CanadianGran she is part of a few groups - book club, ramblers, art appreciation group etc. - so she decided to have a lunch with each group once a month. It gave her something to look forward to throughout the year. Her actual birthday was spent with her large family group.

I would be wary or organising a party, unless you know she would enjoy it.

If smeone wanted me to organise a party for them. I would want to know a lot more information than you have. As you say, you only know some of her friends, so I would expect her DH to draw up the invite list, names, addresses - and send the invitations out. Let him decide what the event will be - tea party, cocktail party or whatever. Then guide him to choosing a venue and getting caterers in to provide the food. Lots of pubs have function rooms and will do the catering and all the hard work - oh, and order a nice cake.

If he is expecting you to organise the invites and do the catering, just say NO.

Why not have an " Noon to Nine At Home" day? You can stagger invites for different groups? I have done this this. Invites can state x will be 'At home' celebrating her birthday & would love to see you anytime between x & y o'clock for drinks & nibbles! '. If each group of pals is invited for a couple of hours then there is time to talk. My family turned up whenever & helped out! Offer glasses of bubbly or non alcoholic alternative and simple canapés, crispy / nut type nibbles to keep it simple. Of course there may be overlap but that doesn't matter. A friend who also did similar ordered in pizza for the evening guests!

You need to settle on a budget and decide who is paying for what, as at least two families are now involved, to prevent any grudges building up later.

I would hate for someone to organise a 'surprise' party for me. I hate being the centre of attention.

Personally, I would rather go away for a nice weekend to celebrate with my DH and keep it low key.

I would ask her what she would like rather than assuming. If she has family, she may prefer to have a small get together with them.

As Urmstongran said, maybe smaller get togethers with her other groups of friends at later dates. If that is what she wants.

If they have a garden and it is June then a drop in barbeque might be a bit less formal.

My DH has always said he didn't want a fuss. We went ahead and organised an afternoon tea with his oldest friends and family from all over the country (pre-covid of course). He was delighted and genuinely moved that people could be bothered to do something especially for him.

Some good ideas from other people above, but I would try to help her OH organise something if you could.

It’s my 60th in January and I’ve been asked what I’d like. I would hate a large surprise party or a fancy dress party. I just love more intimate gatherings with my closest loved ones and best friends. I think she should be asked what she would like. I’d hate for people to feel stressed organising something for me.

I had a "surprise" party and I know no one will do it again. I struggled to even be civil I was so fed up. I'm slightly ashamed of myself but can't imagine what they were all thinking! I'd said I didn't want a fuss making.

Where to start?
I feel a bit overwhelmed.

Now, perhaps I'm being mean but would you ask him to organise a surprise party for your DH?
Why can't he organise a meal out for his wife himself with family/close friends?

Just point him in the right direction.

Urmstongran

When my friend reached 70y she decided against ‘one big party’. Like your friend CanadianGran she is part of a few groups - book club, ramblers, art appreciation group etc. - so she decided to have a lunch with each group once a month. It gave her something to look forward to throughout the year. Her actual birthday was spent with her large family group.

Lovely idea, Urmstongran

Ohhh heck, if your friend doesnt like being the centre of attention, then a 'party' is off the radar, but you say she so deserves recognition, yes, then as others have suggested, a lovely afternoon tea, somehow get the name of 1 member of each group and ask them to spread the word to the others in their particular group. You can do this easily if your friend is on FB ( and ofcourse the others are too )

A lovely afternoon tea sounds ideal, everyone together for a special friend and yes as someone said, if your friend has AC, then it needs checking if they are planning anything.

Whatever you do, i hope your friend has a ☆☆☆FANTASTIC BIRTHDAY☆☆☆

As she has different groups of friends you firstly need to know if the other groups are doing something.

I would keep it small and simple, afternoon tea with your group and not include the other groups.

Would she enjoy a spa weekend with a small group of friends, no more than 4 or just the two of you.

I went away with Mr Stardust on my 60th, for a few days on the coast, in our favourite hotel. Far away from anyone who dared to make a fuss! I just wanted a normal day. Please try to find out if a celebration would be welcome!
If you feel you have to do something, how about organising a group/family visit to a local escape room. They seem very popular at the moment. There's a Dr Who one in Leeds I'm keen to visit!

PECS

Why not have an " Noon to Nine At Home" day? You can stagger invites for different groups? I have done this this. Invites can state x will be 'At home' celebrating her birthday & would love to see you anytime between x & y o'clock for drinks & nibbles! '. If each group of pals is invited for a couple of hours then there is time to talk. My family turned up whenever & helped out! Offer glasses of bubbly or non alcoholic alternative and simple canapés, crispy / nut type nibbles to keep it simple. Of course there may be overlap but that doesn't matter. A friend who also did similar ordered in pizza for the evening guests!

Oh my goodness- what a long day. Id need two naps in the middle

OP, do you even want to organise it?

Id hand the reigns back to him- he who should be organising the party

?

Thanks for all the good ideas. She has been my friend for a long time, we usually celebrate our birthdays with a dinner out with another friend. The three of us chat for hours over dinner, and really enjoy it.

I was the first to turn 60 last year, and I said I didn't want a fuss, plus there were dining out restrictions in place. My family organized a small get together, so essentially two celebrations.

But because her DH has reached out, I do feel I should help him with a bit of a bigger do (and I'm sure he will foot the bill). Our group doesn't usually go over the top, so a BBQ or pub evening should do it. I'll get my thinking cap on, and make sure to involver her daughter as well.

You're very kind CanadianGran - but I do think her DH and DD should be doing the organising, perhaps with some suggestions and input from you.

I think that a BBQ in June sounds wonderful, just have a contingency plan for if it rains, I was thrown a surprise BBQ for my 50th and it was a wonderful surprise, and went on into the small hours with music and drinks and lots of guests, I loved every minute of it! My 60th was during lockdown so unfortunately we couldn’t do much.