PvP:
5x Night Elf Shadowmeld Surprise!
Dwarf: Stoneform can be nice against rogues/warriors.
Humans: Perception and 10% faction bonus

I would go 4x Dwarf (stoneform) for the hunters and 1x human (spirit + perception) for the priest. You can have some nice Snowhite and the 4 dwarves action going there.

PvE:
Draenai: If the +hit stacks it could be a nice boost for your hunters but it is something you can get from gear. The 1K heal would have been OK except for the 1.5s cast and at 70 with decent gear the heal is not all that great.

I would still go with the 4x Dwarf and 1x Human. The 10% spirit for the priest is gold.

Pets tanking bosses:
Yes, your pets can tank bosses. It depends on the boss though. With 4x hunters you can also train different pets with different resists so you have a Shadow Resist pet for Shadow Dmg bosses and a Fire Resist pet for Fire Dmg bosses etc. I think that most of the normal difficulty bosses can be tanked with pets but there are probably exceptions.

CC might become an issue, not sure if any pets have AoE taunts. I also am not sure what happens if you have 4 freezing traps on top of each other, will they all trigger if 1 mob runs into them or will it only trigger one? If the latter then you can just keep your group stacked up but if the former then you will need a lot of micro management to CC. Hunters will need to spread out and each pull a mob to a trap.