New to multi-boxing

[Ughmahedhurtz]

Or you could just Keep It Simple, Stupid and bind a mapped key to your mount key/button such that when you press it, everyone mounts. I've done that since forever and with a decent mount macro, it Just Works(tm).

Example mount macro (from my ISBoxer config):

/dismount [noflying][mod:alt]
/stopmacro [flying]
!if (character in "Hunter") /cancelaura aspect of the pack
#/use Headless Horseman's Mount
/use Horn of the Dire Wolf
/stopmacro [nocombat]
/p Still in combat!

In case it isn't obvious, this macro:
* dismounts if I'm on the ground, underwater, or holding the ALT key
* Cancels everything else if I'm still flying
* Cancels the Aspect of the Pack spell on Hunters (if applicable)
* (commented out the Headless Horseman's Mount since this is my classic macro)
* Uses the Horn of the Dire Wolf to summon my classic mounts
* Stops the macro if I'm out of combat
* If I'm in combat, it announces it to party so I know why someone didn't mount properly (combat is the most likely cause of failure to mount).