Yeah, I can see that. "Activate" maybe? Although that's still a bit ambiguous. That's annoying. I'm actually kinda thankful for the Tome of Battle terminology now.
"While you use this invocation to take a form other than your own, you cannot use other invocations, including eldritch blast, save for those that specifically and directly summon, call, manipulate, or facilitate communication with creatures of the Animal type."?While this would work nicely in a fluff sense, it would be a downright pain to implement mechanically, and I don't particularly think it would be worth it.