Hi tash, could be OT especially if he's having 2 UT naps.
You could definitely try for one nap if you feel he can handle it? That's what I did, I got so fed up with second guessing I just took the plunge and went ct to one nap. There were days occasionally (about once every couple of weeks for a month or so) when I had to force a CN in the car at around 9am for 15mins when I knew she wouldn't make it to her usual nap time. I just picked a time for a nap, EBT if the nap was rubbish and just went for it. It took a little while to find the right time for the nap for her as I realised she started having OT early NW's that we're easy to settle and the nap was getting shorter, so I just moved it later until we found what worked. I'll post a link for you about set nap and BT for you which really helped me. Ideally you pick the time for the nap as you said 11.30, this sounds like a great starting point, (this can be up to 15mins earlier) and choose a BT (say 12hrs after normal wu) and let BT be up to 30mims earlier if the nap was short. Wdyt?
Set naps for toddlers: Why, How and WhenIf it helps what we did was wu 6.30 (sometimes earlier but that was the ideal), set nap at 11.30 to hopefully 1.30pm BT 6.30pm. Eventually this settled quite well until the nap got slightly shorter and we always had OT early NW's. I jumped it to 12pm (same BT) as DD always had long A times in the morning and I knew she could do it. We were there for around a month or so, until be found our final nap time of 12.30 - 2.30pm, BT 6.45-7pm. We actually held that until just recently, so kept it for nearly a year!! Xx