Am I being unreasonable?

It looks to me that they realise you cant really cope with the GC at your house and that's why there's this arrangement in place.
If you get fatigued and don't like mess at your home its best you stick with the way things are.
You dont have to spend £20 on a meal but to be honest that's not a lot t feed 5 people.If you were to take the children out after school you could easily spent that amount and more.
Maybe have a chat about it if you dont want to carry on with this or just dont want the expense of the meal...you could just pick the children up from school and give them a snack and leave when their parents arrive home

Im trying to get your vision of hiw you want it to be.

You want them to pop in unexpectedly, have a cup of tea and a chat and then leave?

Just your son? All of them.? I cant really see that working with the children. What would they be doing for forty minutes or an hour while the adults drank their tea? It might work with just your son but then that eats into the time at at the time he has to spend with his children at the weekends.

Maybe be quite clear about how you see it working before you tell them what you want.

Everybody is aware, for example, that I could not have thd children overnight at my house as just too much for me. I need to say that I value picking the kids up after school, doing the meal etc. I do find it a bit expensive tbh but just keep on going as the relationships are important. There is only me in my house. There is no spouse backing me up and it can be a fight financially. I own the house and am responsible for maintenance/upgrading. I would mean for them all to drop in and would not single out my son to visit on his own. People on here seem a little on the disrespectful side with regard to other people's finances. I think I have done fairly well to keep this arrangement working for about 3 years 🙂

I wouldnt see anything wrong with your son popping over now and again in his own. I see all three of my children on their own at various times. Its much easier than trying to fx it up with everyone.

You are saying they both work, your son from 7.30 am they go away in the camper at weekends, I am sure the children have after school hobbies they catch up with you once a week, when would you like them to drop in exactly, what more would you have to say, that isn't said then , if it's going to be the same conversation over again wouldn't that be boring? Is it because you find the other days long and boring? Try and find a hobby or group to help you overcome that even if it's a coffee morning / afternoon or bingo, if you ask at your local library what is going on I am sure they have a list. Do what ever you are able to do, give it a go. Honestly your family will appreciate you all the more. Also I know £20 sounds a lot but it isn't to feed a five it isnt.

You say the cooking you do is good for you as it doesn’t happen at home so I’m confused as to what the problem is then . You see your grandchildren and your son and daughter in law. I presume it’s because you want them to visit you

Bluebell to say that she should pay for that meal 1 day a week is a bit short sighted. You have no idea how much money this lady lives on and a meal for 5 can cost a lot. But I would give my right arm to have my daughter to ask me over. I moved house to be closer and the invite, without having the GC, rarely happens. But I will take what I can and if having the GC and being there that night is it, I'll grab it. Its not them being rude or mean they are probably just so busy with work and activities for their children that time runs away xx

I would quite like my son to visit on his own, yes, as we have good conversations together. nanny2507 I could drop in on them any time I wanged really. I just would like to have them in my home from time to time.
I'm not bored! I have a very active mind and am intetested in what is going on around me. I currently volunteer for Victim Support and am looking to do more hours, possibly for Marie Curie. I wish I had time to be bored 🙂

You’re lucky to see GC regularly as many of us don’t have that luxury.
I understand you want family to Pop in to see you, but have you told them that?
I also understand it’s easier for you to cook & care for GC in their own home (as they’ll have their own things there) and you don’t want the mess of them coming to your home. But this is maybe why they don’t visit.
Just my opinion