Sorry to hear what you are going through. As has been said, you have enough budget for a pretty decent boat especially if you are in the market for a longer one, as many people are after 57-8 footers. There will be more than enough life-management tasks (eg water, waste, heating, cooking), maintenance, fettling, painting etc to keep you busy. In terms of your mental health I don't think there is much that could be better than actually getting out boating - something you wouldn't be able to do for ages if you were going to take on a £20k project boat. And you'll be able to have your children on board sooner. Best of luck.