Home base for touring Provence with 10-year-old

It does seem a bit far east of most of your areas of interest. Eyguieres seems more central. I suggest checking drive times (I don't know the best app or website for this, TBH) and decide whether you and/or your daughter will want to spend that much time in the car.

We stayed at La Bastide in Saint Didier a few years ago. Saint Didier is a quiet little village with two or three good bistros. The village is small enough that it is easy to drive out for various day trips. We went as far as Aix one day, to Uzes and Pont du Gard another day.

Kirsten,
We always get a Michelin map for the area we are driving in. You can look at the "big picture" to plan your day's itineraries (and plan your whole route ahead of time). Michelin map #527 would cover your area. Amazon has it and it costs about $13.00. One thing we do is to trace our drives and routes on the map and keep it as a souvenir of the trip. We visited a good portion of Provence with our kids when they were 8 and 10, and 18 and 20. On their first trip we stayed part of the time in St. Remy de Provence. Our fondest memory from there is sitting in a small park-like area of town, eating ice cream cones, and watching some senior gentlemen play petanque (Provencal boules). If you can get to the Pont Du Gard, your ten-year old will be very impressed with it. A country market (not one of the super big ones) should be fun for her. A Roman arena can be found in Orange, Arles and Nimes. All may have concerts and other forms of entertainment. You might even come across a bullfight in Arles (no bulls are killed).

Have a wonderful time on your trip! (Also, depending on where you are driving, and if you come across a big field of sunflowers, take note of how they all face the same direction. As the sun moves across the sky, the flowers turn to always face the sun. (That gives them their name "tournesol".) Seeing a whole big field like that I find impressive.
Have fun!

Ansouis is a very charming little village. Not a bad choice, and fairly central to the locations mentioned, especially since the roads around there are quite a bit faster than those deeper in the Luberon.

Just fyi, the drive from Ansouis to Bandol on the coast is about an hour and a half. Bandol is a great little beach town with a small sand beach, a harbor, a carousel right there and a lovely promenade at the harbor. You can take a boat ride out (to see dolphins, perhaps). The market day at the promenade is Tuesday. We really enjoy just walking along the promenade on market day and having a nice lunch. When we took the kids at 8 and 10 they had fun on the beach. It would be a good day trip from where you are staying. There are wineries along the way to taste some of the great rose wines of the area (judiciously of course) and buy some to enjoy at your lodgings. Plus the area is lovely to drive in.

Bandol is not far from Cassis, but Cassis isn't my choice. Others here really like it, so it is your choice if you decide to visit the coast.

I found Aix a pretty laid-back and quiet town, though certainly not a village. Our hotel was near the train station, and the quartier on this side of the Cours Mirabeau was pretty sleepy--a beneficial thing, in my book.