We were in Val D'Isere last week (linked to Tignes). The snow conditions are fabulous, they have far better snow cover than usual for this time of year. I think it snowed a lot before Christmas and over Christmas week and there was a further fall of 2 or 3 inches last week. Even if it doesn't snow at all between now and half term it should be fine in Tignes then.
Look on the snowheads forum. There's a thread there called the view from val disere. In the weather reports section. Steve who lives out there updates it most days with photos. I was glued to it last year.
But I'd have thought it would be fine, it's high up and e space Killy have excellent piste bashers, artificial snow cannons, etc if needed.