Feral druid is a good idea, in theory, but might be a pain in practice. Two melee chars is ... bleh... Either of the caster druid specs might work better, in my view.

For me, I'd say shadow priest.

The "correct" answer, though, is whatever class you want to play... because playing classes that appeal to you is far more important than what is "best". I'd just stick to classes that are more easily macroable.