You might find that you feel more comfortable with OT as you learn more about sensory integration.
I understand not wanting to over-therapy what is basically a normal childhood. For me, that channeled into wanting to find really fun ways to include the kind of sensory input that my DD needed into our normal life to the greatest degree possible. An OT could help with that!
I think that leaving him to find his own sensory outlets is less than ideal. It really sets him up for failure both in meeting his sensory needs and in fitting in with his peers.
Also, for some kids, this gets to be a bigger deal as the years roll along at school. Recesses get shorter. The standards for acceptable behavior become higher. The amount of sensory stuff built into lessons decreases very year. I'd look into now, while it isn't causing huge problems, rather than waiting until big problems surface.
BTW, my DD knows she is on the autism spectrum and she really likes herself. Being like other people is NOT a requirement to like yourself. Not needing extra help doesn't confer self esteem. And Not by a long shot.
One of the things that she is proud of is what a great swimmer she is, and the reason she spent many hours at swim practice each week while she was growing up is that it was perfect for her sensory issues.