A key broadcaster send keys, not commands, not tells, not anything other than keys to other computers (or windows on same computer). So you push '1' and 1 gets sent to the other alts. They can have anything they want on the '1' hotbar. You probably want the shammy to put down totems and then to heal as your 2 most important things. Sure, you can have him attack if you want, but that is probably messy with a hunter. The most important things to remember is boxing is not really easy (or it can get hard) and start small and work your way up. First make a macro that heals your pet or you. You can focus your main then use something like:

[align=left]#showtooltip[/align]
[align=left]/cast [target=focus-target-target] HealSpell[/align]
[align=left]That would heal whoever has aggro, no matter who it is. Then work on figuring out other parts and add them one at a time. It makes it easier to fix if things don't work if you only change a few things at a time.[/align]
[align=left]Good luck.[/align]