There's not a whole lot of difference between two and five, as far as macro's go.

You could macro this with two similar macro's on the same keybind for each toon:

Main's Macro
#show
/cast [mod:shift, target=Alt'sName] Lesser Healing Wave; [mod:alt, target=Main'sName] Lesser Healing Wave; [mod:ctrl, target=Alt'sName] Lesser Healing Wave

Slave's Macro
#show
/cast [nomod: shift, target=Main'sName] Lesser Healing Wave; [nomod: shift, mod:ctrl, target=Alt'sName] Lesser Healing Wave

Note, the main's macro will not heal anyone at all with a normal press, only if you press the macro in combination with a modifier key. The Slave's macro will heal the main with a normal press, Alt press will have them both heal the Main (slave doesn't need to have a condition of "[mod:alt, target=Main'sName] Lesser Healer Wave", because they're already healing the main on anything other then a shift-click.

As desired you can combine, mod and nomod into macro's, in whatever combination you like.

Note, you said "Click" and I have said "Press". Basically if you mouse-click on say your heal macro, it will not be broadcast to your slave. If you press the macro with a keyboard press, your software (or hardware) will broadcast to the other client.




#show
/assist "Method of Choice"
/cast Lightning Bolt

#show
/assist "Method of Choice"
/cast Chain Lightning

This is easiest and simplest. You'd probably want to also have:
Flame Shock (highest total damage shock)
Earth Shock (largest single damage shock)
Frost Shock (snare effect)
Wind Shock (low damage, spell interrupt)

You can do a castsequence for Wind Shock.

Shammy 1:
#show
/castsequence reset=x Wind Shock,

Shammy 2:
#show
/castsequence reset=x ,Wind Shock

Set the X to be the recast delay on Wind Shock.
The first press is Wind Shock #1. If you need another interrupt before it refreshes (the X number of seconds passes) then a second press is another Wind Shock but from the second shammy.





Create a totem stomp macro.
It is a castsequence. Use one entry for each totem you have access to.

I think its something like Earth (10), Fire (20), Water (30), Air (40).
So at 20th, you'd have Earth and Fire.
Adjust the sequence for most important totems dropped first.

I like to use:

Fire: Totem of Wrath, Frost Resistance Totem, Searing Totem
Water: Mana Spring Totem, Healing Stream Totem, Cleansing Totem, Fire Resistance Totem
Air: Grounding Totem, Wrath of Air Totem, Nature Resistance Totem
Earth: Tremor Totem, Stoneskin Totem, Earthbind Totem, Stoneclaw Totem

Pick an Earth and a Fire totem for each shammy for now.
Down the road when you have a lot, prioritize: Tremor and Mana.

#show
/castsequence Tremor Totem, Healing Stream Totem, Grounding Totem, Searing Totem

#show
/castsequence Totem of Wrath, Mana Spring Totem, Grounding Totem, Stoneskin Totem