Whatever is more fun, is the spec's you should go with.
Personally, I'd go pally tank, boomkin, resto-shaman healer and elemental shammies with that comp.
Resto brings Earth Shield and Chain Heal which makes healing a lot easier.
Boomkin adds a lot of dps with Earth and Moon.
With only a single Boomkin in the group, you could check out Fur's post on Balance Druid dps for a good boomkin dps boost.