Paper plates, Popsicle sticks, and a balloon are all you need to play Balloon Ping-Pong. (Not sure how sturdy the paper plates would be, but may be able to do something similar for a carnival/game night social event theme.
More Mason jars.halloween craft: googly eyes, tissue paper, a mason caar and one of those little fake candles that runs on a battery since the residents cant have candles in their apartments. looks simple enough
Balloon Rockets - I've done this in several science camps I've conducted. Kids have fun with it. But, when the balloon deflates it may fall off the straw because it's surface area changes - another good thing to show and explain to kids.
Spider-Mans web at superhero party. The simplest activities are the best with kids! Make a spider web out of painter's tape, let them throw scrunched up newspaper ball to see if they can get them to stick.