Sounds like your buddy is going to be DPS+Healer, so you need to be Tank+2DPS, right?

I'd be strongly tempted by 3xDruids, since they can be Bear+2xBoomkin for you when you're with your pal, or you can go 3xBoomkin by yourself in BGs... OR Bear+Resto+Boomkin if you want to do a holy trinity by yourself and just LFG for two more DPSers later on. If I read you right, you already have a higher level paladin, so you could at least try the 3xDruids out until they reached the pally's level. By that time you may have decided that you love/hate bear tank mechanics and can go do something else.

If your buddy picks a healer that can DPS, you may find it very efficient to just HoT up your bear and then have 4 characters DPSing stuff down through the early instances as you level...

Good luck!