Projects - good idea, keeps the father-in-law busy when he is with us

Jigsaw puzzles are a great thing for several generations to work on at once

Food - plan lots of meals that are things like chili and pasta - big single pot meals (make sure you have some big pots!) Easy to cook (slow cooker is great and frees up hob space) and sociable to eat. If a vegetarian is among the group, you can easily do a seperate sauce for them.

Think about using more canned / dried food than normal - we find refrigerator space at a premium when we have guests, so need stuff that will store well

A long walk is a good idea at least once a day especially with a group of kids - fresh air and a chance for those left behind to have a bit of space.

Take a deliberate 'personal space' every day - defuse before you get snappy with everyone

Switching the tv off is a good idea BUT planned group watching of films or sport or whatever can also put some structure in the day