Could I make these ahead of time and freeze them raw? What's the cooking time under the broiler if so?

You certainly can freeze these chicken meatballs raw. That's a good idea! (I often make double batches of meatballs, freezing half for later use.)

I would let the meatballs thaw and come close to room temperature before broiling; you'll probably need to drain off some liquid that will be released while defrosting. Put them under the broiler for 12 -14 minutes, flipping them over halfway through. ;o)