Ooh, verbs! I like Irene's whistles here because it makes me think airy, tuneful, cheerful thoughts, and also of "whistling in the dark" (click link for a surprise)--just in case this birthday secret turns out to be something dark or dismaying. I also spent time with swims, squirms and erupts--clearly favoring those /s/ sounds. And now I think I can feel a preposition coming on...
A note to players about timing: I'll be posting each day's new word in the morning, probably by 7 am EST, so you can leave suggestions right up until bedtime--which for me is around 9:30 pm. Thanks for all the yummy choices, everyone!