I would suggest Siesta Key in the Sarasota area of the Gulf Coast. This beach is beautiful, white sand, clear water and very nice public beach. There are also many hotels/condo rentals on the sand. However, highrise buildings are not allowed (I think tallest building is 6 stories high) so beach is still very natural looking and not over crowded. There are also many restaurants and activities around to enjoy. It's about 1 1/2 hours drive to WDW.