My two love it but they didn’t go until they were 3 which meant they could go on daddy’s bike on the (tamer) downhills. Last year the then 3 year old was on my bike while the then 8 year old was on his own bike (and dropping his mum on the downhills – mum has requested a longer travel bike for this year).
Lots of pottering about stuff, but Annecy was better when the younger one was 2.
Aquariaz is a fun kids swimming pool in Avoriaz.
Riding the lifts can be fun for little ones and a walker’s pass is dead cheap.
The rest is kind of weather dependent.