If you are looking at Xmas, you may have to rent for the full 2 weeks. Most owners do not like splitting the Xmas vacation because they cannot rent a single week.

Beware, rental prices are at their highest at Xmas.

The area you should look at is on a straight line from St Luce to Le Diamant, about 1 km inland so that you are a little higher that the sea. You should manage to find place with a pool. Look out at the number of rooms and bathrooms and at the reviews. If you go thru VRBO you will get everything translated in English, including the listings on french sites such as ABRITEL. Try leboncoin.fr also.

Another good option is traveling with another family or your parents, you get a better deal renting a big property made up of several houses and a great pool. Let me know if you find this option interesting, I can think of a few good places.