We are not going this week as have already had our holiday in La Rosiere this year
However I can assure you that there are lots of nice things about Les Eucharts (we stayed in cimes blanches appts near Ski Beat chalets)
There is a fast chair lift up to the runs and we never experienced queues. A nice restaurant called La Grange with cow shaped pizzas for the children! There is also a lovely pancake tea room. Also an ice rink and bowling alley.
You can ski over to the main part of la rosiere or take the bus, or there is a short walk through the woods to la rosiere that would take about 15 mins.
We visited the main part of la rosiere and didn't like it as much as it was bigger, more traffic, people. However there is a very easy drag lift in the main part of la rosiere so it is a good place to go in the afternoons if your DCs are too small to take the bigger drag or chair lift in les Eucharts.
Our 6 yr old DS did very well with the ESF ski school in Les Eucharts. 3 yr old fared less well as it was so cold and they seemed to spend a long time standing about in a 2 1/2 hr lesson. It will probably be warmer when you go.
If I were to go back to La Rosiere I would choose les eucharts area again.
Hope you have a great time!