all kids are different. my 3 1/2 has always woken up at the same time every morning from infancy. nap, no nap, go to bed 7pm, go to bed 11pm. none of it matters to her. some kids just have an internal clock.
honestly, i wouldnt cut out a nap at that age. but you can shorten them. i think the 5 pm one is a little late, but if he is going to bed the same time, i say try whichever is more convenient and see how it goes. just so you know, i think if you mess with his naps, he may go to bed earlier, but still wake up the same. you can try it, but most likely less naps will make him want to go to bed sooner, rather than wake up later.
all this aside, most of us moms are thinking how lucky you are because your son sounds like he has a great sleep routine. it sounds like you have lots of time in the day to get things done, and still have your night at a reasonable hour. if he was my son, i wouldnt change one little thing:)