I would not worry too much about snow cover. There was very little over the new year, but snow has fallen since, and more is on the way. Right now, it it still very thin, with only a handful of open tobogganing trails, but snow depths are typically at their highest in Mid-March!
And if there isn't enough snow for tobogganing or snowshoeing, then winter hiking becomes an option.
Regarding your original question: the trails are free. You pay for the lifts - there is a pedestrian lift pass for tobogganers/walkers. And you will want to use them! It is probably a 3 hour walk from Wengen to Kleine Scheidegg...
Mürren is higher but it is south facing, so no better for snow. And it has far fewer trails for the activities you seek: I would stick with the Wengen-Grindelwald area.