My ds is another April'01 child. We have been dealing with the nap thing for many, many months now. What I finally did (after NOTHING else worked) was to just give up. Not the best solution for many, but it has worked okay for us. I don't even offer a nap unless I am sure he will sleep. It became a huge issue and was causing too much stress for all involoved. I didn't like what it was doing to our relationship or how I was mothering him. Something had to give, so I chose the nap.
Now, here is what we do now.......if ds has had a really long or busy morning we will spend some wind down time, usuallly we start with painting or colouring then progress to reading a few stories. If he seems receptive to the idea of sleep I will sell him on some "quiet time" in the bedroom nursing (I only do this if I know he will sleep, once we've committed to the bedroom we don't get up again until he naps otherwise he will just try to get up again every nap/bed time for weeks to come). If I think he won't go easily (which is most days) I set him up with a snack and a video (one of the only times we do videos) just so that he has some time to recharge. Now that we have been doing this for a while he will actually ask for a snack and video when he is starting to get tired on occasion. He will even put his head down on the futon while he watches (won't doze off though) and really rests. Those days he just won't nap, but will likely end up going to bed early.
I wish I could say this was a great system, but it does have its advantages. He will fall asleep by 7 or 8 most nights without a nap so dh and I get to enjoy our evenings together (when he does nap he will be up till 10 or 11). Unfortunately, even when he is really, really tired he will sometimes refuse all attempts at sleep so he will crash out at 5 pm which messes up our whole schedule. Also, many early evenings are spent trying to devise ways to keep him up another half hour or hour so that he will sleep till morning. It also makes it difficult for us to make plans for the evening as ds will often need to be in bed half-way through family gatherings. Plus LLL meetings are in the evening, so we can't go unless he has napped. Those days I try to exhaust him in the morning with even more physical activity then usual in hopes he will nap, but it doesn't always work.
Don't know if any of this will help, but at least I can offer you the knowledge that you are not alone. Keep trying, and I am sure you will come up with a solution that is at least somewhat workable for you