Choose colours cobalt blue, alizarine (or madder lake, raw sienna and neutral tint (or paynes grey which has a little more blue)

beware the neutral tint will give a very strong dark colour

Founex farm1   founex farm2   atmo tree final
Roughly sketch the composition, Seat your people in a group not in separate groups.   Turn board around and paint around the heads with a pale blue. Dry then add in background hills

 

  

Paint in the shadows with a grey purple. Don't over think the shapes. Add darker areas under the tables
Founex farm1   coppet beach3   coppet beach4
Paint in the bodies blending the colour together and allow to run, avoid painting discrete shapes   Roughly put in hair then faces with 1 stroke of sienna + madder

 

  

Paint in darker shadows under the table and rough shapes for legs. Add the foligae for the tree and the trunk and branches
Founex farm1   Add boats and more branches in the tree. Be careful about adding the face of the woman make tiny dots first and note that the eyes come half way down the face