6 years old
Toss beanbags into a large cauldron.
Large cauldrons or containers
Party guests toss a bean bag into a large cauldron (or large container). Soft balls work as well, but beanbags are often the preferred choice, and limit the injuries and accidental breaking of things that sometimes happens with hard balls.
Another variation on this involves cutting out a shape of an animal or thing for participants to throw the beanbags through. For example, a big toad (Trevor) or Firecrab or whatever Potter related animal or item you would want can be cut out of cheap plywood, then made holes for it for the kids to throw the bags through. This is easy to make (just a scroll saw will do it) and you can be as creative as you would like with the paint/decorations as you would like.
Other variations are possible, one can be called a “Quaffle Toss” using Whiffle Balls or the like into a bucket. Whichever version of this game you choose, you can play this game over and over and rotate groups easily all night for those in the stores or libraries.