How are the wishes in a will upheld?

You need to make a will and I would recommend seeing a solicitor to explain what you want asap , There are ways for half of your estate to go to your children rather than your DH getting it all .
My DM was in the same situation when her father died . He remarried and didn’t change his will , so his new wife got everything, which she left to her niece on her death .

You need to see a solicitor. Lots of charities offer to write a will for free. Yours is more complicated. I think you can leave your half of everything to your children but if it is a house you can specify that your DH can live in it until he dies. But as I say see a solicitor to do it properly. Cancer Research UK are offering a free will service.

Please go and speak to a solicitor. Both DH and I are divorced with grown up children and I was determined that my children should have half of the house etc (as was DH), especially should I die first and he remarries. The solicitor was very helpful and has provided us with wills to reflect our wishes. I'm not sure whether a free will from a charity will cover everything you need, but I may be wrong.

Hot foot it to an appropriate solicitor asap! Good luck.

I think you must be clear who will be executor of your will, made via a solicitor. If you have concerns about your husband handling the money it may be safer, though more expensive to make the solicitor the executor.

Definitely use a solicitor. After 45 years of marriage my husband had an affair and I left. We had mirror wills, self written (as my parents had, and their worked perfectly so I thought ours would too).
The first thing I did was go to a solicitor to change my will! She was so helpful in advising recording etc.
In these uncertain times, I also felt it important to make provision for my will to reflect what should happen should my children separate to guard their children’s inheritances.

You must see a solicitor. If you own your house jointly a very simple document can change the method of ownership to tenants in common in equal shares, if that’s not what you are at present. This means each of you owns half the house. You could leave your half to your children (and you can encourage him to do likewise) but, if you wish, specify that your husband can live there until he dies or goes into care. He could make a similar will. He could change his will after you died, or it would be automatically revoked if he remarried, but he would not be able to sell the house acting alone because he would only own half, your children the other half. I would advise making a solicitor or your children executors rather than one another for additional peace of mind that the will will be administered according to your wishes.

Definitely a solicitor, for both of you. Explain your wishes, in lay terms, as you have here, and they will explain your options, as GSM has said. It can become more complex, as discussed several times on here, so I think you need a proper amount of time to discuss the ramifications.
I think you are confusing 'wishes' (such as I'd like my friend Jemima to choose a keepsake) and specific bequests (to my friend Jemima, my collection of odd socks).
As I understand it, 'mirror' wills are a lay term, simplifying what a couple wish to do. So glad that your mum finally realised what she needed to do!
As to who ensures it, that is the executors who make declarations to the Probate Office (GSM, please correct if I'm wrong)

The executors swear an oath to administer the estate properly, yes Nannarose, but I wouldn’t appoint someone who I thought might not comply with their oath!

I will only support all those who say go to a solicitor. There is no other solution.

Totally agree. There is no other option. Go to a solicitor and get it all done properly, then you will have peace of mind.

I think your solicitor would sort out the issue of your children being impacted by a second husband quite easily with new valid wills.

That is exactly the situation for me and DH. You need to see a solicitor but we found it fairly simple. Everything in trust for the children (his and mine) which they get after the demise of the second of us. Our children have known this from the day we married so that they wouldn't worry. Also because in the distant past DH lost all his family heirlooms when his stepmother left the lot to her children.

In these days of blended families and step children your situation is not unusual and will be easily dealt with by a solicitor, who can also be an executor should you think that appropriate.

Just to think about - as well as the scenario GSM has described, you could leave the house completely to your children, specifying that DH could live there until he died HOWEVER you need to make provision within that for him to be able move to a more suitable house, go into care etc.
All of these things are do-able, with the right advice. So time to dig out some of those savings!
I am an advocate of DIY wills when they are very simple (I have done 2 in my life where there were no complications at all) but gone to a solicitor twice when things were more complicated. I would say, please don't use a 'will writing' service - a proper solicitor is needed. Both times we have made solicitor written wills, they have given us a draft and a simple 'lay' copy to go away, think about, and amend.

Yes get a solicitor to write a will and be aware that wills can and are changed by unscrupulous people.

If your parent remarries or a long lost cousin appears to (look after) her/him, be very aware your parent is vulnerable to having the will changed. Or get power of attorney to make any sort of financial arrangements they wish.

I have been close to two attempts to do this, one was foiled, one cost the family £500k.