Here are the value studies from the sketches I posted previously.
The one above I think worked out pretty well. I may move on to color.
In the ones below, the value study highlighted some difficulties.
In the first there isn't enough variation in the values; but I can make some decisions and add some midtones.
This last one has too much light value. It's also not such a good composition, I think.
Weirdly as I painted it I became more interested in the chair than I was in the people, which made me think I was on the wrong tack.