You start at Venosc / Le-Bourg-d’Arud and do around 1200m of climb up to Lac Muzelle and the Refuge on the lake, where we slept for the night. The refuge is staffed for 4 months of the year, from June-September, and provides evening meal, breakfast and a bed for around 35 EUR. They also have beer and wine available, and can provide a pack-lunch (if you order it the evening before you need it). During the rest of the year I think the lower level is open for hikers.
The walk up to the Col du Vallon (2530m) is another 550m of hard climb on a good path, with a steep series of switchbacks as you get to the Col (not recommended if you have a fear of heights). Once you’ve got to the top of the Col - it’s almost all down from here - and there’s lots of down (1750m) to go.
Descending on the other side of the col starts out gentle, and then proceeds to get steeper. There are some sections of the path down where you’ll need to do a little scrambling, but nothing too serious. I would not however want to do this path in the rain (as the rocks will be slippery), or with small children. I’ve marked these sections with a red area on the map.
As you get down to Lac Lauvitel, you’ll find a good collection of townsfolk chilling out by the lake; and then a long and uninteresting walk back down an almost cobbled path to Danchere. From Danchere, it is a 3.5km undulating hike along the river to get back to your car at Venosc.