Hi Annette!!!
Congratulations on your FIRST Walt Disney World Vacation!!!
I, too, have a three year old so I have lots of experience in what attractions a three year old can and cannot ride. Your twins will have a blast and I can't wait for you to experience Walt Disney World with them!!
I think that you will be pleasantly surprised at the number of attractions that your three year old twins can ride. The "magical" height to ride the big kid rides is 40 inches. I know that our son was able to hit the 40 inch mark when he was about three and a half, so hopefully your twins can hit the height also.
Forty inches is the first major cutoff for most of the rides. There is only a handful of attractions that require a height over 40 inches. Please see the following link to the
Walt Disney World Attractions Height Chart for a detailed list of the heights for various attractions at Walt Disney World.
I am so excited for you and your family!! Please let us know if you have any additional questions!!
Have a magical trip!!
Scott