Personally, I believe sending the form is enough of consent. However, currently there is probably no lawyer who dares to say that officially. Everybody is still too afraid.
Sure, as long as you've shown the mandatory "request presented in clear and plain language to provide consent by an affirmative act (such as checking a box online or signing a form)"[1], make it clear that sending the form is considered consent, and describe explicitly the process by which such consent can be revoked.
