Was there last year:
When you say "westernmost" are you thinking of hiking from the Marseille side of the Calanques, and then kayaking the next day from Cassis? I can't speak to the hike from the Marseille side. I hiked from the center of town (Cassis) using the trail map that you can get at the TI (right next to the main beach in Cassis), which was easy to navigate. The hike itself was straightforward, well-marked (color-coded paint marks on rocks to guide), and there was only one section that was technical but not hard. You start from town on a main road and have to turn onto another road. That was actually the hardest to figure out, but with the map and some pointing by locals in response to my confused look, we found the trail-head just fine.
Here's what we did: we actually (we being my husband, 3 kids, and me; ages, 47, 46, 14, 12, 9) rented an outboard motor boat for 9a-ish in the morning (because we were concerned about our 9yo's ability to kayak all the way out to En Vau), BUT, there was SO much fog that we could hardly see 5 ft. in front of us, and the water was SO choppy, that between the fog and the chop, I wanted off (I wanted to hike anyway, but gave in to majority rule). So, after boating almost all the way to En Vau (hard to tell because of the fog), we turned around, went back to the harbor where I and my 14yo daughter got out and proceeded to hike to En Vau where we met up with my husband and 12 and 9yo's who turned the boat right around and went back out in it. The younger two LOVED the boat. So in the end, I hiked out to En Vau (you pass the other two en route) with my daughter. It took us about 1 hour 20 min from the center of town. We spent the day cliff jumping (there is a 30 ft cliff on the left side cliffs when you are looking out from the beach), and then all took the motor-boat back at the end of the day.
We spent only one evening, one full day, and one morning in Cassis. That one day was SO fun, we would have stayed another if we didn't have plans.
So I think your plan sounds good. It sounds like you are emphasizing the hike from Marseille (which I think takes a bit longer and thus you will see more) the first day, which will prevent too much repeat.
As for the Luberon, Roussillon is a favorite. And I would definitely go to the Abbey Senaque (very near Gordes. Go first thing in the morning). We stayed in Isle sure La Sorgue, which is near Fontaine de Vaucluse, both on the western edge of the Luberon and beautiful. You will see more towns as you drive to the Cote du Rhone from the Luberon. We took the backroads from Isle sur south through Lourmarin en route to Cassis and eventually Nice. We saw many villages that made us want to live there, or there for a month next time.
As for restaurants, we favor middle-eastern fast food type places - lots of schwarma, falafel. WE found one on the boardwalk in Cassis that we returned to twice. You can also look at Yelp or trip advisor before you go and just bookmark several to reference when you are there. I do that often, as searching for food everyone can agree on with 3 hungry kids is no fun