I searched the rules forum, but couldn't find the answer to my question:  Can Fire (fire/ice) target multiple things, but deal dmg to only a few of those targets?  Example: my opponent has a 2/2 creature in play, misdirection and a blue card in hand and I want to destroy it using fire.  Can I play fire targeting both my opponent and the creature, so that it cannot be misdirected?  Also, on a related note, do I need to assign damage as the spell is cast, or can i assign damage as the spell resolves?  

Thanks in advance.