I have a dreamstate druid in my mixed 5's team.

Her macro's look like this:

#show
/assist ProtPally
/cast [help] Rejuvenation; [help, target=targettarget] Rejuvenation; [target=player] Rejuvenation

I have a macro such as this for Rejuvenation, Swiftmend, Lifebloom and Regrowth.
If you were deeper Resto, you'd add in other heals too.

Her heals are bound to my numpad keys.
So its very easy to heal with the druid... if the target is friendly they get the heal, if the target is hostile its target gets the heal.
You could adapt this to the shaman too, but I think due to mobility the druid is the better choice for healer.

I went dreamstate, because I have only one druid on the mixed team and would like the dps boost when killing weak stuff.

Messing around with aura's/stances.... Mashable macro's to active Ret-Aura, ShadowForm and Moonkin Form which won't break those forms once active.
-- Paladin /cast [nomounted] !Retribution Aura
-- S.Priest /cast [nostance:1] Shadowform
-- Dreamstate /cast [nostance:6] Moonkin Form
The druid heals or priest if I really needed it, and pressing the Aura macro button anyone not in form for the next pull goes in form.






*EDIT*
I'd assume 3x Elemental Shaman, should be able to keep your Prot Pally up with ease.
As in druid stays Boomkin and Shaman's stay Elemental.
If you were changing one, I'd go Druid as healer, but 3x Elemental can heal fairly well even in heroics.