The airfield restaurant is pretty good, too.
The one time I visited Biscarrosse airfield there was a restaurant, but I was told they only serve the local flying school. Has that changed or is there another restaurant, that I missed?
Regarding seaplane flying: there are precious few dedicated places in Europe, though it may be implicitly allowed in certain countries. Most "official" places seem to be in France! But recently my own country added one too.