do you have something you have been putting off, like sorting photos and getting them in albums? clipping and filing magazine articles? sorting and storing videos and DVDs?
what about a take-off on one of the DIY shows like trading spaces - each of you decorate a room on a limited budget (like under $10) with just what you have on hand or can scrounge.
clean sweep, each choose a particular space to clean and organize
DD and her then fiance, now SIL, invented and designed board games and sold them at shows when they were poor college students looking for good date activities.
found art contest - kids can join too
as an outgrowth of the clean sweep type activity a basket or bag of junk for each contestant. have a set time limit to come up with a sculpture (or mechanical invention) using the found objects in your bag. winner gets to keep one of the items he owns that was in the “toss” pile after the clean sweep.
my oldest daughter and her hubby and kids would never have to leave the house to find fun, as they create elaborate betting games based on just on televised football, but every televised sport imaginable, with goofy rules and prizes, seeds, “playoffs” etc. For instance on Nascar you pick an advertiser and get points everytime a car or driver with your company’s logo appears according to preset rules (lap leader, on an interview etc).
in this house, if you tried those DIY activities together you would end up killing each other or divorced, but as a competition with teams and idiotic prizes, it works for us
if you have kids in scouts, try to invent goofy merit badges, with requirements, activities, tests, badge design etc, and then hold races to see who earns his badge fastest.