Hmm, perhaps finish the starter area then move to Durotar / Razor Hill and quest from there, or even grind the Quillboars, mobs in the caves to the East? of Razor Hill to ~10, then move to The Barrens.. Or quest up to a certain point individually and just use an instance summoning stone to gather them all up and go from there(RFC / WC / SFK) though i can't quite recall the minimum level to use those, level 10 or 15 i think.

Also dont forget that for each of those races you have a relatively short run to the Zeppelin that'll drop all your character's off in Org / Tirisfal Glades and TB.

If i were to run a mixed grouped like that, i would probably just autorun the Orc and Troll to Razor Hill, while taking the Zeppelin to Org with the others, and then run those to Razor Hill also - Then grind at the Fortress outside Razor Hill to ~6, and start questing or grinding Quillboars or the higher level mobs to the east? in the caves to 10 or so, then move to The Barrens around then.