I wouldn't sic your dog on them. Like Laura's Babies said, it would only come back to bite you in the ass (pun intended) should your dog bite anyone. Call the cops and report it. This way if they decide to set fire to something else, it's on record and the cops know who to go after.

I lived in an apartment complex on the 3rd floor. Kids who waited for the bus would go into our lobby and reek havoc on the doorbells, including mine. One morning I got totally pissed off and ran down to the lobby in my pjs. I took the kid by the collar of his shirt and hussled him down to the bus stop (which was a block down the street). I told him if any one of them pulled a stunt like that, the cops would be called. PROBLEM SOLVED!!! Nothing comes between me and my sleep!!!

If I were you, I'd talk to the parents of the kids with the kids present. If that's not possible, refer to the first suggestion of calling the cops.

Good luck. Any way of possibly disconnecting the doorbell and putting up a door knocker or something???