I'd prefer the 5 paladins. You don't need a dedicated healer until you get to cataclysm dungeons.

grab yourself a keyboard expansion to get more keys (like a x-keys or a g15).
Assign a key where every paladin heals the tank, assign a key where everyone heals himself
(/cast [target=tankname] Healingspell) (/cast [target=player] Healingspell).

Control with your tank and 'interact with target' and /follow to move your toons.
Just blast through the first instances.