Sorry you had to join the club but welcome just the same.
My 4 yr old is also a type 1 diabetic and was dx'd when he was 26 months old. He started pumping about 6 months after diagnosis and I highly recommend looking into an insulin pump at some point once you get more used to the the disease.
There is a great site for visiting Disney with type 1 diabetes at:
http://www.allearsnet.com/pl/diabetes.htm It was written by some folks who also post here occassionally (Zurg and Zurgswife).
If you haven't already, I HIGHLY recommend checking out the Children With Diabetes (CWD) website at
http://www.childrenwithdiabetes.com They run an annual conference which next just HAPPENS to be at WDW - being held at the Coronado Springs Hotel in July 2007....called the Friends for Life conference. It is for parents and kids with type 1 and there is lots of great info for the parents and fun for the kids who have their own program. We attended last summer and plan to go next summer (this summer it was also in Orlando but at Seaworld). Since you are rescheduling your trip anyway I would definitely take advantage of that opportunity.
The CWD website also has a great forum at
http://forums.childrenwithdiabetes.com/index.php I think you couldn't do better than to join up and chat with us over there - lots of folks with preschoolers and type 1 - including me!
I will send you a PM with this message too - feel free to PM or email me back. I'm happy to answer any questions!