Even though we had stayed in Bercy Village before, we didn't know about the Musee des Arts Forains, and I feel like a fool for not having gone sooner.
Do your research so that you can book the right tour on the right day, but you won't regret it. They let you know in advance that the tours are in French, but there is literature there to walk you through the place in different languages. And even if you don't use them, just walking through the place looking an everything would be incredible. (on the day we went about half the group were non-french speakers, so the guide did much of the tour in English, but I wouldn't expect this)
This historic place not only showcases decades of games and rides, but they have been preserved so well that you get to interact with many of them. I had never seen so many of the games before, and getting to be able to play them made or an amazing experience. But it is not just games, there are rides here from long ago that you get to experience.
I couldn't recommend the museum more highly and would encourage anyone in Paris to go.