With 8 adults and 4 kids under 5, I'd stay at Boardwalk and buy hoppers for the adults ONLY. I'm not sure that's possible - like the whole Dining Plan thing where everyone in the same room HAS to have the same DP, but for some reason, I don't think everyone in the room has to have the same ticket.
My reason - Usually, kids under 5 are gonna hit a wall, and be wiped out at night. If you are all related or good friends, I'd feel out the adults on this concept:
ALL ADULTS: Wake up early, have fun with the kids at a park.
SOME ADULTS: Get the kids back to the room at a decent hour. Dinner and swimming, and whatever other fun, then to bed. I'd suggest night activity at the hotel - most offer something like movies or scavenger hunts, etc. I'd also suggest having them all stayand hang out in one room to amuse each other as only kids can do, and then being moved back to their own rooms later after they fall asleep.
SOME ADULTS: Go out for night fun (WALK TO EPCOT OR HOLLYWOOD* in just a few minutes, or uber / bus to the parks further away.)
Lather, rinse, repeat.
If they are all gonna be under 5, you'll all have a blast with them in the parks during the day, and hitting the pools, but sometimes, I think the parks at night with kids that age can be more trouble than the payoff, all in all.
I'd present this case to the other adults in the group. Kind of like tag teaming the night activities with the kids, and giving some adults the option for kid free adult time. The kids will probably not miss the adults that go out at night at all. They'll be having too much fun with everything else.
*This is where hoppers absolutely rock. If your travel time to a park is 5 minutes or 10 minutes, hopping after a hotel break is...well, magical. If you KNOW you'll be taking a hotel break, might as well get a hopper if the park you were at is a zoo, and a diff park is empty.