The easiest will be a focus based approach.

Each toon has a macro, on the same keybind as your maximizer PiP switch key, as the toon who's window you are switching to.

So if your hotkeys are Shift F1 and Shift F2, for window 1 and 2 (in Keyclone), then both toons focus the first toon on Shift F1 and both toons focus the other toon on Shift F2.

Then every character can have a follow macro, on the same keybind.
Basically goes:
/Follow [target=focus]

And each toon can have similar DPS macros.
/Cast [target=FocusTarget] Nasty Spell

And heals can be:
/assist [target=Focus]
/cast [help] Nice Spell; [help, target=TargetTarget] Nice Spell

Plus you can have toon specific heals, which aren't focus based.
For example Numpad 1 will heal toon 1, Numpad 2 will heal toon 2.

If you haven't made your toons yet, I'd go for a Resto Shaman as healer.
Normally Priest/Druid are my top choices for heals, but without heroism/bloodlust already on the team, I'd take a hard look at the shammy.
The pally is lacking an AoE heal and is an immobile healer.
The shammy is immobile to an extent (Riptide and Earth Shield can heal on the move), but the shammy adds AoE healing (Chain Heal).
Priest has Holy Nova/Prayer of Healing and the Druid has Wild Growth.
But a shammy has Wrath of Air (spell haste), Tremor (fear protection) or Strength of Earth (Str/Agi buff for pally), Flametongue Totem (spell power) and either Health Regen totem (if Pally blesses Wisdom on the casters) or Mana Regen (if pally gives Sanctuary/Kings). Plus you get Heroism/Bloodlust every 10 mins, which can be huge for bosses.

RAF is good.
I'd do a chain link, something like: A -- B -- C -- D -- E
Boost several teams during RAF.
It will give you more options down the road.
You would get a lot more teams leveled if you boosted with the DK.
And for every two sets of toons you boost, you get a free 60th from granted levels, from whichever account to the account previous to it in the chain.

For addons, the only boxer required (well not required, just extremely nice) addon is Jamba.
No essential key settings for a predominantly caster team.