If it were me, I'd choose a pally as my tank. They are much easier to get avoidance cap and they can easily aoe tank mobs which reduces the need of cc. Also, pally tanks along with druids do a decent amount of damage even in their tanking specs so that is something to think about. As far as a healer - shamans add a great deal of utility with heroism/totems/purge/interrupts and can double as dps. Just lay out your options and pros and cons of each and decide what would serve your group best with synergy spells/talents and what you would have the most fun as. Prot pally, 2x mages, spriest, resto shaman might be fun imo. You will probably never run out of mana mana stream/spring + blessing of wisdom + vampiric touch. And you got chain heal/healing wave + vampiric embrace for heals. 2 mages for cc and great dps. Tons of utility with purge/heroism. You get totems and blessings as well.