Driving through France (route nepolean)

I am traveling through France at the end of May (for our holiday) with
my family (wife, 4 yr old and baby, grannie and grandad) from Calais
all the way down to Cannes. Because its going to be tough on the
children, we have decided to break the journey up to try an make it
bearable. We are staying overnight prior to departure from Dover and
driving to Lyon the next day for another overnight stop. My first
question to anyone who can help is how busy is the main motorway from
calais to lyon at this time of year (especially around Paris) and is
this possible to achieve this distance in say 9hrs. The route planner
indicates 8hrs travelling at approx 60mph average. Am I right in
thinking that the roads should be relively clear as they are toll
roads ? or is this naive.

The next day I would love to drive from Lyon down through Grenoble to
Sisteron and along the route Napoleon to the coast. How long will this
take me ? How much extra time is it to go this route than it would
around the alps along the Rhone Valley autoroute ? If its only an
extra couple of hours then it would be worth attempting, anything more
and its not worth it. Does this route get busy ? is it very hilly as
my heavily laden people carrier might struggle ? Would anyone not
recommend this route ?

Anyone who can offer me advise I would very much appreciate it