T.R.
Hi L.,
I am a dental hygienist. At that age he should only be using toothpaste without Fluoride. You should also help him with brushing his teeth once he is done. We don't usually recommend fluoridated toothpaste until he is 3 years of age(a very small amount) or can spit out the paste and not swallow when he is done. Kids his age now tend to swallow and fluoride isn't good to ingest , it will upset stomach and can cause vomiting.
Hope this helps. I think it's great the fact that he is brushing, it really helps when they cooperate!! Good luck!