Raven69David,
My husband and I were in the same boat a couple years back. We'd been going for years, between conferences and our own trips and now we had the kids to enjoy. It was great fun!
Two things from my limited experience (2DSs, 2yo and 5.5yo): make a plan to have some running around time. There are many playgrounds, splashing areas or climbing spots in each park. That way, they don't mind as much when you're pushing them around for a while in the stroller.
Remember to take breaks. Mine were great nappers and would nap in the stroller at home, but with all the activity, we sometimes just left the parks and took them back to the room. If you can't do that, a quiet corner near the parades is fun, or find some of the outdoor entertainment where they can sit and snooze, you can take a break and everyone will feel refreshed.
Other than that, there are many wise and experienced parents on the Families board and you will find lots of suggestions on these topics.
Enjoy your trip! -Skip