Actually that depends on how much my 70 shamans participation will affect the scenario. If mob xp is still ok with 2 70ies I'll do the 2 lvl 70 shamans + 3 newbie shamans and do a combination of instances and questing (mostly questing and then instancing from 30 to 46ish (SM/ZF) and then again from 48 to 55 (BRD).

If having 2 level 70 in the team affects xp from mobs too much I'll either swap one 70 shaman for my newbie pally or just stick to questing. The good thing about levelling "just" 3 chars is that the collection quests will be a lot more viable, and with a 2*70 escorte, ganking should be at a minimum.

Also, I can to the moneymaker instances one more time (Underbog up to first boss and Sethekk up to and including first boss).

If you're starting from scratch and just have the three accounts and no powerlevellers questing is the way to go - even with powerlevellers questing is probably faster (although less fun, hehe).