Is it ok for a 14.5 year old to participate in a half or full marathon jog?

Well I plan on running the Seattle Amica Half or Full Marathon in November 2010 if my physician is ok with it. I'm going to be training all the way up to the marathon and already have a marathon training program selected. I wouldn't be attempting a speed run but would be jogging it. I know I'm motivated enough to do this. I'm not obese, quite fit (can run 3 miles in 22 min, 5.02 first mile). I have been running seriously for about six months. My parents are both physicians and my mom said she would probably be ok with a half marathon and would consult colleagues but didn't have any idea about a full marathon, and we would have to go to a pediatrician. I don't plan on going overtly fast either. I know I'd stop if I was hurt etc... didn't feel right