Some posts are a bit harsh, this isn’t AIBU! On the other hand, I do get the underlying WTF? sentiment.
OP - your musings aren’t wrong. I can often spend time thinking of random ways I’d like to help people if I had a lottery win. It is not always Lady Bountiful thinking, it’s often thinking of situations you’ve been in and making it easier for someone else to not go through that.
However, I don’t think it’s a good idea for you. You need to sell at the best price and then use your share in the best way to benefit you and your children.
Am not expecting you to divulge figures, but am finding it a bit hard to imagine how this couldn’t help you purchase your own home. A £200k deposit is a significant amount, are you in an insanely expensive area of the country? How much is your rent per month vs what a mortgage could be?
If a mortgage really is never going to be possible, and no need for you to explain why, then I’d be looking to invest the proceeds fairly safely for the benefit of your kids. Maybe keep £10k in an easy access account - to be kept as an emergency fund. Put £5k in another easy access and use it to have fun experiences with your kids. The rest, I’d spread across the best fixed-term accounts you can find, bearing in mind the £85k per account “insurance” if a bank goes bust.
You may not be able to utilise the money now re a mortgage etc. But using it sensibly could mean that your kids get more choices later down the line in their lives. TBH, you’d be a bit of a dick for not putting them before some random family.