Oh I see. Yeah, I wouldn't want to take my little one past, 5-6 meters, even if he could...Yes, it is with guides. There are a couple of easy dives, but also a couple that can have current and are a little too deep. So definitely doable. But Ko Haa inmo would be a combination of a fun and safe OW dives. You can then take it from there.
As I said int he OP, our only experience with diving is in Belize. We didn't go too deep (max depth was around 5-6 meters IIRC).
We might just focus on snorkeling.