Ahhhh! The memories! I have 11 cousins on my mother's side, and no two of us are more than a year apart in age. (My grandmother joked that for a period of time, it seemed as if every time she picked up the phone, one of her children was calling to say another baby was on the way!) Our holiday gatherings were always at my grandmother's "house", which was actually a large apartment over the store that they owned in Philadelphia. Can you imagine that mob scene? There was a large kitchen/dining area, a large living room with a black and white t.v. in the corner and ONE bathroom. My grandparents' bedroom was on that floor, too, and we were allowed to go in there and crawl on their high bed and under it. The boys usually played some sort of stalking game in there. Upstairs were two large unused bedrooms and a rooftop where my grandmother hung clothes. And to add to the fun, they had a mutt dog, there were 10 adults, and oh yes... this establishment was at Front and Diamond Streets. The "el" runs right by, so every few minutes the roar of the train would add to the noise in the house. Yet it was so much fun. And today when my cousins and I gather with our children, we still laugh about it. Our parents actually allowed us to go play on the roof unsupervised! My goodness! How did we all survive??
But, to get to your question, of course you do need to make sure the fun and chaos are safe. One of the things that we did as kids, and that I did with my own children when they were growing us is skits and songs. Every holiday included a little "show" by the children. We used to spend a good amount of time planning our performances. We'd lip sync to Monkees songs (yes, I'm VERY old!), do little skits, tell jokes, etc. I've been a cub scout leader for many years, and I still incorporate this into our large gatherings. In fact, you can google "cub scout skits" and you'll get tons of ideas for helping to organize a little show. Try to find a space where the kids can prepare and tell them that it's a secret and a surprise for their families. Get them started telling some simple jokes. Have them act out some scenes. Perhaps even the 1 year old can serve as a happy "prop" who waves or claps hands at the appropriate moment. This will also give the older children a chance to lead the younger children. The older ones can do most of the speaking, and the little ones can follow cues. You'll definitely have to supervise but once it gets going, you might even be able to leave them on their own for a while to think up their own "acts". They'll use their imaginations and will be busy without too much chaos, hopefully. Of course, this won't keep them occupied for the entire day, and you can be sure that at one point they'll be running headlong toward that glass curio cabinet. But, it should keep them busy for a while, and provide for great family memories years from now.
And then there's always lettuce ball. LOL One of my cousins had five children of his own. When things got chaotic at his house, he used to put a head of lettuce in a plastic bag and toss it into the yard. He'd yell "Make some salad kids!" and the kids would kick that bag all over the yard until the lettuce was just mush in the bag. What can I say? Sometimes that's all the creativity you can squeeze out of an exhausted parent's mind. LOL but the kids loved playing "lettuce ball".
In any event, enjoy Thanksgiving. You'll probably only have another couple of years of complete chaos with the kids. Once they all start getting near to 8, 9 and 10 years old, it'll be a different kind of wild activity. And not long after that, all that happy energy turns into a gathering of adults around the table who reminisce about the craziness and fun they had as kids.