To help with your choice, unbiased (largely) snow reports and weather forecasts can be found via this link:
http://snowheads.com/ski-forum/snow_reports.php?
Les Gets definitely ticks all the boxes apart from altitude. However, I just had a look at the snow report (the unofficial one, not the tourist board one) and they're having great conditions there and the entire PDS area right now, so it'll probably still be decent by half term.
Les Gets also...
With half term being only 4 weeks away, you may be limited with your choices.
The good news is that there's been loads of snow the past week, and all resorts have established a good base of snow (it was looking a bit dodgy up to early Jan).
Also, high resorts tend to be purpose built.