We are driving to Grand Massif this Feb half term. Our plan is to try and get as close to the bottom of the mountain by Friday night as possible so we have a less hellish journey up on changeover Saturday (hopefully we'll beat the busses up from Geneva).
We need a motel type place or affordable hotel which can accommodate 2 children and 2 adult with secure parking.
There's an Ibis and an Ibis Budget (v cheap and cheerful) at Sallanches, so very close to the Grand Massif - not sure which date you'd need. Many years ago, we stayed in an Ibis in Annemasse en route to Flaine; I think it's still there, but there's also an Ibis Styles along the road that do family rooms sleeping 4, and you get a free breakfast as well, so might be worth a look.