Remember - epilepsy is just a word that means that someone has a tendency to have recurrent seizures. First seizures are often not treated because many people have just one seizure in their lives, and most of them do not go on to have a second seizure. However once someone has had 2 seizures, the chances that they will have a third (and more) gets much much higher - it's about 75%. Add your son's abnormal EEG to the mix, and it is very very likely that he will continue to have seizures. No one can say now if it will happen next week, next month, or in a year, but statistically it is very likely that it will happen at some point - not a certainty, but very likely.
If he is having tonic-clonic seizures (it sounds like he is) they are extremely dangerous if he happens to be on a bike, on the stairs, in the bath, etc. So avoiding that type of seizure is extremely important. Moreover, there is some evidence that the more seizures you have, the more the brain is likely to have seizures - it's called "kindling." So your son's best chance of ultimately being seizure and medication-free is to nip this in the bud now.
I do understand your reluctance to have your son on medication for something that seems to be only a sporadic issue. My daughter's first seizures at age 15 were 3 tonic-clonic seizures in one afternoon - which was completely traumatic and scary and of course we put her on medication (Keppra) right away. But after I did some reading I learned that 3 seizures in one day are statistically the same as one seizure, and so I questioned the diagnosis of epilepsy. She stayed on meds and had no more seizures for 7 months, but was having a bad reaction to the Keppra (it is generally well-tolerated, but she had some existing anxiety issues that worsened on it), so her doctor suggested coming off of the medication to see if she might have been misdiagnosed. We had 7 great weeks without medication - and then she had another seizure, and we now we had no more questions in our mind about the epilepsy diagnosis and her need for medication! And then unfortunately things got much worse over the next few months: she had multiple tonic-clonic seizures, began also have simple partial seizures, and is now on 2 medications without complete seizure control. So you just don't know how this is going to progress, and there is no way to tell for sure based on what has happened so far.
I am grateful that we did try taking her off medication because I stopped questioning whether or not she had epilepsy. It was horrible and upsetting when her seizures returned - and we were very lucky that I was close by when it happened so that she did not injure herself - but at least we had clarity about what we needed to do. It sounds to me like you just don't have that clarity for yourself yet, and I do think that is very important.
Everyone's situation is different. For instance, a 4-year-old child is very different than a 15/16-year old: you have much more control over his activities, and can keep an eye on him constantly if you need to, while my daughter needs her independence, wants to drive, will be heading to college soon, etc. So you may be more able to safely "take a chance" and postpone medication.
But you also need to grapple with the fact that your son does have epilepsy (he has had 2 unprovoked seizures) and that his seizures + his abnormal EEG make the likelihood of more seizures very high. Do your research, ask the questions you need to ask, and then make the best decision you can. And good luck - this is a hard road, and nothing any parent expects to deal with!