Parachute
Playing with a round parachute may be old hat to adults, but it's new fun for many toddlers and is unusual in that it works with large groups. Focus on developing gross motor skills, rhythm and cooperation. A large sheet or other large cloth will work if you cannot find an actual parachute, but remember that a big part of the attraction for kids is being able to lift something very large. Everyone stands around the parachute and holds on with both hands. All together, you can lift it over the children's heads, bring it back down and watch how it balloons in the middle, and even invite the kids one by one to dart across under the parachute to the opposite side. Be careful of trips, falls and frightening entrapments under the silk.
Animal Charades
Toddlers enjoy pretending, so games that let them act out being something else are often hits. An adult may need to start this by imitating the behavior or sound of some animal, gradually adding more characteristics until one of the children names the animal. The correct guesser gets to perform next. Be prepared to suggest an animal if a little actor gets stumped for an idea.
Puppet Hunt
Hide all but one of a stock of hand- or finger-puppets, at least one per child, while the children are out of the room, but don't hide them too deeply. When the children come in, have the left-out puppet talk to the children from behind a table or child-height screen, explaining that all the other puppet friends are hiding and asking the children to help find them. (If they're hiding rather than lost, it's less frightening and encourages the children to do their seeking stealthily.) As the children find the puppets, your puppet can invite them behind the screen to chat about where the other puppets might be. For a party, the found puppets could be taken home as favors.