My kids had the flu last week and gave it to me!! They all had different symptoms, some had fevers of over 102, my oldest dd was throwing up and all of them had coughs. The only thing that would concern me about your son is the sleepiness as none of mine were unusually sleepy. I might call the doctor if I were you just to be safe.
My own symtoms right now are low grade fever, cough and stuffy nose and I believe it is the regular flu but I can't seem to sleep even with nighttime cold medicine!