It is also likely that your LBS will have a special tool to try and straighten the hanger first. It is a relatively simple task and may cost less than a new hanger provided it isn't damaged or doesn't break during straightening.
I would have them straighten the hanger and then determine if the derailleur is okay or not. I just went through something like this with a Specialized 24" kids bike. Friend was transporting it and it fell against the derailleur. Used the tool at the bicycle coop and once it the hanger was it good shape I could tell the derailleur was tweaked too and needed replacement.
Good luck and the fix should be quick and pretty inexpensive.