Decision to NOT medicate after 1 seizure/abnormal EEG

Please help..My 12 year old son (will be 13 in a couple weeks) had a tonic clonic seizure on May 9th.  It lasted less than 1 minute, he recovered very quickly.  He is an honors student, no behavioral issues, normal neuro workup/normal MRI.  His EEG was abnormal showing "Primary generalized" activity.  The Dr. wants to start Keppra. I am so overwhelmed.  The side effect of Keppra is "behavioral issues".  He will be going through puberty in the next year or so and puberty is such a fragile time in one's life.  I don't want to start this new med at the same time.  He has only had the one seizure and by definition epilepsy is 2 seizures.  I know his EEG is abnormal, but can people have abnormal EEG and NOT have seizures? Has anybody chosen to wait to medicate after 1st seizure with abnormal EEG? It is so hard because he is older that I see most kids when they present with their first seizure. And he has had no other seizures (absent/myclonic..) PLEASE HELP. I don't want to do the wrong thing.  Oh and he wants to be a Navy Seal and medicating him will prevent him from doing this.  If I don't medicate and he never has another seizure then he can join the military. I am struggeling with medicating and then asking myself "what if" he never would have had another seizure.  Thanks so much in advance