Our third day was spent hiking in Argentiére, towards the huge Glacier of the same name. We took the cable car to Lognan, and then hiked to the start of the glacier (route 16 below). A very easy and quick hike, ideal for hiking with kids.
After lunch we decided to take the Grands Montets cable car to the highest point (3275 m) where there's an excellent viewpoint. It was windy and cold, but the views were amazing.
Later that evening, we decided to try one of the local restaurants in Vallorcine, L'Arret Bougnête, located next to the train station and our hotel. It offers a lot of savoyarde specialties and the ones we tried were quite good (the desserts were equally nice).