I wouldn't publicize it as a bonding event - just a social night or a family fun day. Do more smaller events and maybe one or two big events for the year. That way there are choices, something for people to attend if they can't make one particular date, and not a ton of work for each one.
Our schools do an adult spelling bee or a trivia bee once a year (district-wide) to raise funds for the educational foundation (teachers can apply for mini-grants $250-500 to fund something special in their classrooms). Each elementary school does one big ice cream social with either a silent auction or a Scholastic Book Fair at the same event. There's a family fun day in good weather on a Saturday (face painting, games, sometimes a little petting zoo from one of the local farms or alpaca places, some simple competition with 3-legged races and so on), and a pizza fundraiser at one of the local restaurants that gives a percentage of sales that night to the parent organization.
A family movie night might be fun - consider doing it in pajamas to make it unique, and then the kids are ready for bed when it's over. You could sell popcorn/snacks. You could even have 2 rooms with 2 different movies to cut down the noise/chaos.
A family pot luck sounds fun - but add an activity (maybe a raffle or some games), same with a doughnut event (you can't just have unhealthy foods especially for the kids with issues like diabetes).
It takes planning, but you could consider a school garden - kids learn where food comes from, they use math skills to calculate seed/seedling purchases, they do graphing to plan out rows, they learn the science of seed germination and photosynthesis...and they get out into the dirt and fresh air. This would be for next year because you'd need the teachers to buy into it, plan curriculum tie-ins, and line up donations/advice from a garden center. But the planning committee is a great bonding experience!