judy, thats great!  he will be fine, i played football for a year in high school and growing up i raced bmx for years and years.  it will be good for him, and he can do it.  im sure he knows his limits, and since the coach is in the know, if ryan says enough for whatever reason, im sure the coach will listen to him.   if ryan is anything like i was, when i was in the games i pretty much focused on the games, and never felt tired or anything until it was all over.  i tried my best to stay hydrated, and with what i know now, i would suggest ryan drink a gatorade or powerade type drink before and after practice, get his glucose up and add some extra salt to his system.  good luck to you and him.  i hope he enjoys the games, i always hated practice.

take care

ian