Take your tank to TB and help heals while the 4 grind out some levels.
Skip the collection quests in Mulgore. There are a handful of kill quest there.
Killing knolls and the one in that cave/mine area--Venture Co & some Supervisor.

You'll also have some type of collection quest killing dwarves in the north (west of TB). They drop some axe that you need to break and they drop it at a high rate. Grinding there is pretty good too.

The wells quest are easy also as the stuff spawns fast as you kill the mobs around the wells.

I skip the harpies also. Just focus on getting to level 10, grab the 2 RFC quest form TB.
Run to barrens and take flight paths on the way. There's some good kill knoll quests here to.
And work on that Shaman Fire Totem quest.

Get to Ogrimmar and it's flight path. Do the Thrall quest for some LT. This is a pain drop, but good grind non-the less. So you'll have 2 more RFC quest. Bind in Ogrim.

Take the zep to Undercity and get the last RFC quest, it's in the same room as the paladin trainer. Hearth to Orgrim.


Hopefully your paladin got some levels, 17 to 19. Now 5-box RFC with that tank. Complete the quest, and grind some more of this instance until your lowbies are level 14 at least (or 13.5) then turn in the RFC quest in Ogrim, TB and UC.

From 15-20, I'd do Barrens quest. It should be fast as your tank is higher, and your lowbie shamans will catch up faster.