Sounds good, but I think I'll have it happen when you type "RIGHT CLICK" on the keyboard. (including the space)
One should not be so cruel to the poor one button mousers.
Yeah, or Mac users could just join the 20th century, and buy multibutton mice. That's what I did.

I have seen several solutions to one-button-ness in various games and apps. Some use menus (which makes no sense in a game like Aquaria), some use modifier keys (ctrl is the standard, and is the default at the OS level (yes, OS X supports right-clicking for contextual menus as the OS level)), some use a click-and-hold scheme, and some use some combination. In IV's game Darwinia, click-and-hold is used to perform the functionality of the RMB, but in Darwinia, the RMB is only used to change unit states, and click-and-hold isn't used for anything else, really. Shift is used as a modifier key for certain functions, however, such as firing squad weapons. Thus Darwinia uses two strategies. From the videos of Aquaria that I have seen, a modifier key makes sense. Doesn't really matter which one, though I would suggest that if the keyboard is used for anything else, the appropriate modifier either be user assignable, or in a position easily reached from the other keys. Also, while I am sure you wouldn't do this, make sure that multi-button mice are still supported on the Mac version, as there are plenty of us with multi-button mice.
xander