Congratulations!
We left the GH Cannes yesterday and could not rave more. If it were me, I would choose either Nice or Cannes rather than moving over and over. As a Hyatt Diamond, we were treated exceptionally well and I can say that having breakfast outdoors, looking out over the Mediterranean, well, it was magical. A truly magnificent hotel.
We are now in Aix en Provence - our base for five nights. We have a car and really could not imagine doing the area without it. Not sure of your reason for not doing it but you might wish to reconsider. We had already chosen Aix for a number of reasons and had a hotel reserved when suddenly, Marriott announced a Renaissance Hotel was opening in Aix - and that's where we are. Nice to be able to do another hotel on points. Aix is a wonderful city and has been a great base. Can't speak to Avignon, sure you have your reasons, but we love it here. We go to Avignon on Tuesday.
As to Marseilles, we avoided it totally. Did not really hear great things about it and saw no reason to go. Perhaps we don't know what we're missing but no regrets.
Either way, this area is truly magical and I'm sure you will have a wonderful vacation made even better by the fact that its your honeymoon!