you should heal only and not moonfire/starfire/wrath. your shamans can do enough dps so save the druid's mana for healing.

healing:
set up your keys so that each button targets a different party member to heal. (ie. F1 heals tank, F2 heals shaman 1, F3 heals shaman 2, etc)

tanking:
keep the keys seperate from the shamans. you can hotkey maybe a few (consecrate, seals, and hammers/judgement). soon you'll get evenger shield if you dont already have it plus hammer of the righteous and holy shield. use those in your hotkeys. things like blessings, taunts, and healing can be clicked.

dps:
drop your totems in rotation with each shaman. /castsequence works fine for this. one button.
lightning bolt, chain lightnings, shocks, etc goes on another button or two.

thats it. you shouldnt have too much problems with it. your pally should have the most buttons with your shamans spamming their dps spells only. think of your 5 characters as one person, one unit. they dont all have to do the same things. that's why you dont starfire with your resto druid.


edit: sorry i just read 1 shaman. well its the same concept. tank with the pally, dps with the shaman, and if you ever need to, heal with the druid. simple. things will die fast anyway.