We just got back from DL on Monday and I say it was way cold. I'm from Texas and it felt like December to me. Especially at night. I say wear jeans and a t-shirt and bring a sweatshirt along to put on in the evening. My DD wore short sleves once for about 3 hours but as soon as the sun went down and the breeze started blowing it felt colder than 50 degrees.
At any rate, we had an amazing time as this was our first family trip to DL and Easter was a blast. I hope you have just as much fun as us.
I'm already looking for ways to return soon.
Jennifer