Hi JeannieL,
If you are staying for two weeks in Menerbes and have a car you can easily make a trip to Aix for the day during this time. It's a pretty but touristy town and quite a bit bigger than Menerbes and the other lovely towns you will be near (Lourmarin etc.) so it's nice for a "day in the city". The markets are indeed great, as is the experience of sitting on the Cours Mirabeau and watching the world go by. There are also good Museums in Aix. And if you like art or architecture you can visit Cezannes studio (by car) which is great - tiny but insightful and so perfectly tweaked to suit what he needed as an artist.
Marseille is a totally different thing - last time I was there was some 9 years ago (before it was the city of culture in 2013) and I think it has changed /developed a bit since then, but it is a very big, quite grubby place, so prepare yourself for that! It's wonderful too - but does take a bit of getting used to in my experience. There are lots of good North African influences such as amazing pastries (Baklava etc) and Notre Dame de la Garde is very unique. The Calanques are amazing as Christian Said, and the Panier is a lovely pretty spot. The port is also great for people watching. You can take a bus from the centre of town (perhaps around the port) and head toward Point Rouge which will take you along a beautiful coastal road to the sleepy little point at the very edge of Marseille and right near the Calanques.
If you're driving in Marseille, fait attention! It's a bit crazy
My favourite thing about Provence however is wandering through little towns like Menerbes and doing day trips to other little places nearby. There are lots of good "chateaux" (not like those in the Loire, but Provencal versions) in the area and some are furnished which makes for a great visit.
Enjoy.