Well, those actions can not be triggered in the game client from the same keypress, so you need to send 2 separate keypresses. Plenty of keyboards and mice have the ability to set such a thing up, but this might end up problematic since the software might round-robin to the next client after the first input. I'm not quite sure how different ones would interpret it. Might also be down to whether or not it's really the configuration software that is handling the macro, or whether it's in on-board memory on the device itself.

Additionally while I think a simple rebind of 1 = 1+2 with no delays for the actions is probably fine, there is no way of saying for sure that Blizzard will see it that way, especially with how trigger happy they seem to be currently. So be aware that there is always a level of risk involved when you add in another piece of software/hardware, even if you are technically within the rules.