This has also happened to us, although we're a bit older and it was due to the loss of immediate family.
We've paid off the mortgage, and will move soon, into a home of similar value so will remain mortgage free.
We've given some to the children - not a huge amount but enough for them to do things they have wanted for a long time.
We have bought property abroad, somewhere that has given us a lot of lovely house and land, for not an awful lot of money. This has been a wonderful investment in terms of quality of life. It's a resource for the whole family to use whenever they want, and we will spend lots of time there. The house probably wont increase much in value, but it wasn't bought with that in mind. If we need to increase our income at any point, we can rent it out. It will also be something to pass on to the children.
The last thing we bought was a motorhome. It has been life changing. The freedom it offers is incredible, and although it used up a hefty chunk, we have been to some incredible places. I'd really recommend it and just thinking about it is making me smile.
We have also given gifts to charity and also to people who were particularly important in our family members' lives.