In April you'd definitely have better chances in southern
Spain in the
Med. Less
wind, smooth seas, and temps in the mid 20's.
Option 1:
If you took out a
boat from Alicante you could see all the great coast from La Costa Blanca down to Almeria where you have some amazing nature reserves (Cabo de Gata being the most amazing). Many of the best beaches, like Playa de Los Muertos, are best accessed by
boat so a charter yacht is the best choice for this region.
Option 2:
The Balearic islands. A cheap flight to
Barcelona is easily found and from there it's just a quick shot over to Mallorca or Ibiza. Both of these places are great for families with many amenities and activities on hand.
We're from Valencia and the temperature here routinely hits the mid to high 20's in April.
If you have any more questions about the region,
diving or charter just check out our website as we have quite and extensive guide to yacht charter in
Spain.
Good luck!