yes, there are very serious charges to be concerned with. Depending on all the circumstances, I saw first or second degree felonies. Then, as to SOL; they vary. At least on of the 2nd degree felonies was 5 years. The person being underage can affect the SOL. The first degree felonies don't have an SOL.
as to the "I didn't know"
bottom line: you need a lawyer.794.021 Ignorance or belief as to victim’s age no defense.—When, in this chapter, the criminality of conduct depends upon the victim’s being below a certain specified age, ignorance of the age is no defense. Neither shall misrepresentation of age by such person nor a bona fide belief that such person is over the specified age be a defense.

