it's a very nice holidays home  very close to the sea (0,5 km), in the city La Tranche sur mer (in Vendée). Just have a look on videos !!

http://www.latranchesurmer-tourisme.fr/decouvrir/
In the region Vendée, look at : https://www.vendee-tourisme.com/
If you like islands, La tranche sur mer is face to "lle de Ré" (re island) about 45 minutes boat. You can visit it by bicycle !
 
The weather is very nice during summer. You can swim every day. The sea isn't dangerous at all for little children. There is a sail school where you have lessons of optimist (little boat for children), catamaran boat for tee-agers and adults), wind surf, paddle, surf and kite surf.
http://www.cntranchais.fr/.

If you like attraction park, several of them are close to our house:
O Gliss Park : http://www.oglisspark.fr/
Indian Forest (Accrobranche, Paintball, ...) : http://www.indian-forest-atlantique.com/
Il you like futurist shows, the Futuroscope is about two hours from house

A historical park, one of the best in the world, just amazing http://www.puydufou.com (about an hour from La Tranche).

ILa Tranche is also very close to "marais poitevin" (30 km). You can get a wodden boat and sail on the march.

 
Very nice cities near La Tranche : La Rochelle : 1hour - Nantes : 1h30

Don't miss the Island of Ré,called the "pearl of the Atlantic coast". You can reach it by boat ( 45mn) from la Tranche and there rent a bike. It's wonderfull. And don't forget the best ice creams "la Martinière".