What I'd do is grab a pair of the $10 original-only boxes (or $15 battlechests if you REALLY want goats/belfs) and RAF those to a pair of your existing accounts, letting another pair's subscriptions lapse temporarily (time this depending on what time is already paid for so you don't waste it). Transfer out of the new accounts if desired.

I'm working on a similar class setup, mainly so I can swap out the tank or play with different dps classes when I feel like it (also, use them for AoE, although maybe shamans will be better at that in a patch or two). Druids for a fun-pvp group...obviously lack shamans' strengths vs fearbombs and diseases and so forth, but they're amusing. More so with starfall and with the new in-combat shadowform...which I believe allows for things like "SF-flight/travel form" macros (bugger the 2m CD, but that hardly stopped AP-PoM-Pyro "three minute" mages).