Those hats are fantastic! Thanks for sharing the pictures.
As for purple being appropriate for boys, well, I think a hat (and especially your helmet hat design) will work fine. After all, it's a baby, right? So who's going to quibble about the color.
But if you think the purple for boys is a big issue, could you incorporate more green into the hat, say in a bear design maybe or in some other boy design (can't think of what, though)? What about doing something like "It's a boy!" in green, or is that overkill?