Off the top off my head I would recommend:

https://www.cite-sciences.fr/en/explore/permanent-exhibitions/cite-des-enfants/cite-des-enfants-2-6

https://aquariumdeparis.com/en/

https://www.parczoologiquedeparis.fr/en

https://www.jardindacclimatation.fr/en

https://www.lemondedenoe.fr/

https://philharmoniedeparis.fr/en/philharmoniedesenfants

https://maps.app.goo.gl/dk5ReQsW5v9YHHF6A

I need to go to bed, so I'll need to come back later and elaborate and drop some more tips but those options are a good starting point.

Thank you all for the recommendations, we’ll give (some of) them a try

Go to museeums, they are pletora. There plenty of cool stuff/experiment for kids on the musée d'histoire naturelle but there is plenty other on every theme in Paris.

You should crosspost this on !forumlibre@jlai.lu to reach many french at one time.