You ask me about what to do with Kids in Paris. Do the tours! Take a Bike Tours or River Cruise.
If you love the nature and want to show your kids how the Parisian kids spend their childhood, bring them to the Luxembourg garden. A beautiful park with a great playground, a fountain pond for sailing small wooden boats, a marionette theater (puppet shows at 2:30, 3:30, and 4:30 in summer), an old fashioned carousel (designed by Charles Garnier, who also built the Opéra), and very amazing playground.
You can see a lot of old men playing chess under the trees and one man with big collection of boats which your kids can have for 5 euros and play with them in the fountain.
The garden opens his doors at 7.30am. It's a best time to do a photoshoot in Paris. You will really appreciate your time together with Paris photographer in the empty beautiful area. To get a cute Paris photos don't forget to be well dressed. This place is the most gorgeous place in Paris.