This is really good for young families as there are facilities for decent cooking and washing, down stairs is a games room and a Carrefour city less than 100 metres from the apartment block for the basics and more. It will be a bit cramped for 4 and the pull-out bed is functional rather than comfortable, but the bunk beds are great and the bathroom sufficient. But hey, you are here for the beach (15 minutes walk), the town and the adjacent environs, so you will not be staying in much. Eating out in SJL was very reasonable and sometimes heavenly.
We had a great time exploring, visiting La Rhune is a must, we walked up (not for the faint hearted) and trained down: many do it the other way. The views are magnificent (1000M) and the facilities on top very handy. We took trains to Biarritz and Bayonne, visiting museum’s (Basque history), ate well and generally relaxed. The Atlantic was surprisingly warm to dip into. Other picturesque towns in the Pyrenees are nearby as well as a saunter to Spain: San Sebastien, Bilbao, the Guggenheim etc.