No doubt, others will tell you an afternoon nap is required.
the funny thing is, the kids in our family, unless they were sick, have always been oddly flexible in their sleep tolerances. Beyond infancy, they have also always been very tolerant about eating times. We must be a fluke!
As long as we used a stroller, the kids in our family have been very flexible. At WDW, they have an amazing ability to get by on less sleep and irregular naps.
Then, you know your child best. I'm sure many children do best when they stick to regular nap/meal times.
then again, I've seen a few threads where parents got blasted because their kids fell asleep on the late night bus ride back to the hotel. While driving the bus goes dark. So it hardly seems fair to me. Most the adults also fall asleep riding the midnight bus back to their hotel! At the very least, most folks close their eyes.
When we do a party, we found it smart to eat a light meal about 3:30pm (a great option is Gasparilla Grill at GF. Arrive about 2, see the Gingerbread House, photos, relax, eat, hop on the monorail. Arrive just before 4pm.
Get your cookies early (do they still give out cookies and cocoa?) You will be going against the flow- get your dessert early when the lines are short.
Late, you'll probably want another snack. That's a good time to hop into Starlight Ray's. Again, no lines.
When the party is over, let the stroller napping begin.