Emme, it looks like you are getting more than you asked for here. If you want to wear long dresses for religious beliefs, go for it!
As far as the rides go, I agree with Dizzy4Dizney, just be sure to tuck the ends of your skirt into the ride before it starts. We try to go to WDW in the cooler months (relatively cooler...this is Florida afterall) and my wife has worn a dress to the parks and did not have any problems.