Your alts want to be Ranged.

Your main can be whatever you feel like playing.

**Edit**

Sorry, in my above post I was tired and didn't really read the question. You will probably not be doing instances with just the 2, so plan around killing normal mobs as efficiently as possible.

I would go Prot Paladin, with the shaman laying Windfury Totem, Fire Nova Totems and Chain Lightning to wipe up groups of mobs while the Paladin keeps himself full of HP (Seal of Light + Reckoning + Windfury).

With this setup, you will stick around the area affected by the Shaman's totems for longer periods of time, utilizing them to their potential, rather then killing a single mob then moving to another area, out of the totem's Area of Effect.