Keep in mind that further east you travel in the Mediterranean, the longer the season and the warmer the weather.

April is good one-month early for places like Santorini, Mallorca and the Italian coast in terms of a beach holiday.

You might consider the island of Cyprus. Mid-to-late April should in the middle to high 70's in Eastern Cyprus, and probably in the low 80's in Ayia Napa and Protaras in Western Cyprus. And Cyprus is filled with some great sandy Blue Flag beaches (best water quality).