Outdoors - go to the old standards of sack races (collect old pillowcases from friends or go to the dollar store), relays, wheelbarrow races (one kid holds another kid's legs and that one walks on hands), potato-in-spoon races, etc. Split the kids evenly so it's not all big kids vs. little ones, or give the little ones shorter distances. If it's warm, water balloon tosses are good - again, shorten the distance for little kids. Absolutely pick up every shred of broken balloon as they are hazardous to birds and small animals. Egg tosses are okay if there's a way to wash off but that's best in the summer with bathing suits & sprinklers.
Indoors or out - limbo dance - you can run 2 poles at once since you are having a small army of kids. Otherwise there's too much waiting in line. Kids of many ages enjoy musical chairs but you need something for those who are "out" to do while the rest of the game continues. Again, you can run 2 groups.
Go easy on "prizes" because it's expensive and you're already in deep for expenses, and also because it gets too competitive with kids being sad if they don't "win".
Get an assortment of sandwiches to accommodate allergies and individual tastes. Pizza is often a favorite. If you get cupcakes, they can be decorated differently and that can be the "theme". You can buy or rent a little cupcake stand to display them, and attach a couple of helium balloons to it, and you're done.
Otherwise just get a couple of nerf-type frisbees or balls, so no one gets hurt in a crowd that big, or some hula hoops, and let them play on their own.
