Weather permitting I would sail east to the “Calanques” the first night or drop the anchor north of the Riou island.
The I would sail further east to Cassis and spend the second night. Nice anchorage down the Cap Canaille, little bit rolly depending on the weather.
Then I would sail east again to “les Embiez”.
You would have 2 days left to go back to Marseille, you could spend the last night in The Frioul island, in front of Marseille.
If you are in the mood for a ~10h sailing you could go straight to Porquerolles Island which is a beautiful place.
Be carefull with the Mistral wind, blowing W/NW and can last for 2-3 days.
Hope you will enjoy,