I know for few options:
a) Nin - Sabunike: Thermical wind, not so reliable, beach for kids, shalow water. Surfmania Center Nin, Kiteboarding Croatia - School Rental & Shop
b) Neretva or Viganj: small, nice, thermal wind, good food, rural. Water Donkey Windsurfing & Kite Center VIGANJ-CROATIA, Kiteboarding club Komin
c) Bol:no school
Lefkada: Good for families, good food, nice beaches. camping-village-episkopos, Villaggio Maistro. Kite Club Greece
3. Italy Sardinia: Punta trettu, Porto botte, Porto Pino.
Nice beaches, great food, .... Kite Village Sardegna.
For all places you have to ren car to be movable. My family spend 13 days in Lefkada month ago and we had 9 windy days. We use from 7 to 17 qm kites.
Last year we also spend 14 days in Lefkada and In Punta trettu.
While El Medano would work pretty well for you know that it's not an amazing kite destination, much more windsurfing oriented. The kid friendly beach is a 600m walk from the kite beach. The atmosphere and food are great.