The Cite de Science was good, but maybe a bit disappointing. There were some fun interactive displays, but it was geared towards kids that really like science. There weren’t any guides, or audio tours in English, so we may have missed some things. I would say this is an individual call, it is a bit outside the city, and is not included in the Paris Pass, so if your kids are really into it, plan a half day trip there. You can also combine this museum with going to Montmartre, it’s not far, just a few metro stops away. Montmartre makes a good place to do some walking, and climbing stairs, and the area behind Sacre Couer is great for finding a small bistro and a creperie, and also a bit of souvenir shopping, which the kids enjoy.
By the way, the kids loved riding the metro. Don’t be afraid to try it, the metro is very well organized and not hard to get around at all. The Paris Pass includes a day pass for all the days you activate it, and it does work, so this was one feature that we thought was valuable. But, it doesn’t cost much to buy day passes or roundtrip passes, it just saves you the hassle.
Since the Louvre is a must, I find combining it with an amusement park works well. So, I’ve done the Louvre, particularly the Mona Lisa and some of the 15-16th century portraiture and the paintings by David, which the kids love to figure out the stories, but you will probably need to pick a section or so. I find 2 hours is the maximum I can get with the boys in a museum. The treat for after the museum though can be the amusement park in the Tuilleries Gardens, right outside the museum. In the summer, there are rides and arcade games so a bit of fun for the kids. And, just a good long walk thru the Tuilleries with their ice cream stands and festive atmosphere is nice for breaking the day up.
We also really enjoyed the Grevin Wax Museum. This took up about 2 hours, as we took tons of photos and had a lot of laughs, there were amusing statues for the kids and the parents. Nearby is the Chocolate Museum, which is one you can skip. Really had no value. But do the Wax Museum, it was a lot of fun.
If you have time, try to go to the Centre Pompidou as this is a fun attraction for kids to ride the habitrail-like escalator and see a bit of fun, modern art. You can have lunch outside in the plaza across from the Centre, and again, lots of lively street entertainers. Another place to dine close by that is nice for the kids is the Latin Quarter, near Notre Dame. There are streets filled with outdoor small casual cafes, that have local cuisine, but also kid friendly menus.