I have been in your situation with my 2 year old,who use to wake at 3am full of it and nap at 10am for 30 mins or so. I just stopped her naps during day and kept her occupied during day and she now goes to bed at 7pm until 7am next morning. It took a few weeks for her to stop falling asleep during the day, but we finally made it!! I hope this will help.

You are probably correct about him phasing out the second nap.

I would try to put your son down for a nap before he becomes overly tired. Typically, small children become tired about 3-4 hours after waking in the morning. And I would try to get him to bed earlier in the evening by about 15 minutes earlier each night until he is getting to bed by 6 or 6:30pm.

I read the book "Healthy Sleep Habits, Happy Child" by Marc Weissbluth, and it really helped us.

My daughter always woke up early every morning no matter what time we put her to bed. So when I moved her bedtime to 6pm, she slept until 6 am and still took a one hour nap at about 11am each day.

It may take a few days to get his sleeping hours adjusted, but it is well worth the effort. I had a happier toddler when she got enough sleep, AND she did not fight going to bed.

Good luck!