My son was also diagnosed with epilepsy age 5. It was a terrible, terrible time in our lives. So I know how you feel.
My son was on lamictal, and it worked beautifully for him for many years. Around age 9 or 10, he was switched over to topomax, due to breakthru seizures on the lamictal. At age 12, he was taken off all medications, and has now been meds-free for almost 2 years. No seizures!!!
One of the worst side effects on the lamictal at age 5, was behavioural changes. My happy, contend little boy turned into a cry-baby. He would be soooo unhappy, and cried about everything and anything. It was really, really, really tough, seeing that change. It got a little better after 3 months, and I'd say in time it probably balanced out. I can never 100% say how he would've been in those formative years without meds, because children do go through phases and changes. But he did cry much less after some time has passed. So he did get used to the meds. Oh, it also had an effect on his bowels, and he got a rash from it which dissapeared without treatment or changing the dossage.
Good luck!!