We see griefers of all ages in the MMOs we play and the kids games are no exception. We've discussed before how games like Toontown Online take steps to prevent griefing with canned chat phrases and passworded friend features. The worst thing a toon in Toontown can say to you is "You stink!" which is really not very hurtful. But it is rather bothersome when it is spammed at you until you are able to escape the griefer, say by going home and gardening. .
Disney has taken steps, however, to help with the Toontown griefing problem. You can now turn off Friend Invites in the Options screen so that you can't be spammed with them. There are also new options when looking at another toon to Ignore griefers and even Report them.
Funsuckers will always find a way, of course. They'll get on the elevator in a building and then jump off just before the doors close so that you end up going in with less people than you need to be successful. Or they'll jump off the trolley just before it goes in, so that you won't have a full group to play the trolley games. Or they'll join groups and then not attack so they don't get aggro, but can still complete their Toontask (quest). No matter, what Disney does, they can't stop the need of all Funsuckers to suck your fun. But at least they are trying and we are grateful.