Hi Kelly,
Yes the darned catnap! Some days they'll take it and some days they'll fight it. BTW, congrats on your great nap day the other day!
I don't know if you have read this yet, but the catnap is a freebie. So what that means is that if you are having trouble putting him down for it in his cot, try a walk in the stroller or hold him in your arms, or go for a car ride. Just about anything you can do to help him get a little extra sleep to make it for bedtime.
If you still are having trouble getting him down, then what you did the other day was great. Just keep things really mellow and very light activity as to not overstimulate him.
HTH!