Keep it physical, and underground...
I'm kind of in the same situation, but I'm still deciding if I should go for it or not (I'm not the 14 yr old), since I got a lot of opportunities and 14 really IS too young, in my opinion.
Unless the girl is super mature and very hot that she doesn't look 14 at all,that would be the exception. However, in 99.9% of the cases, they're young and immature, and you don't want that except for the ass.
If all she has is the booty, try to keep it hidden, or else you'll get a molester reputation.