Hi our ten year old is very active in travel soccer, swimming and tennis.  We double dose her on hot/humid days of soccer and that does not always help her enough.  A few times we have tripled her so she can compete.  She tires easier only when it is hot, but I would recommend you ask your endo about the increased doses.  I know some of the other parents do this.  I like swimming the best since she never seems to get hot, but she refuses to give up the soccer.  She does get headaches which I think are usually related to eye strain/eye glass issues and sweats a ton.  We have found hydrating the day before and up to an event like a tournament helps.  Our endo says we should keep her active and try not to limit her, that we can manage her to be able to exercise.