Are they into shopping/flea markets? If so, go to the Marche aux puces, which is a funky collection of used stuff dealers:
http://marcheauxpuces-saintouen.com/1.aspx
Head to Sacre Coeur at night and watch the artists.
Go to Versailles and check out the fake Austrian village Marie Antoinette had created when she lived here.
Climb the Eiffel Tower.
If they like fondu, go to this funky (but touristy) place in Montmartre:
https://www.tripadvisor.com/Restaurant_Review-g187147-d779422-Reviews-Le_Refuge_des_Fondus-Paris_Ile_de_France.html
You don't mention your kids' feelings towards architecture, but Notre Dame is definitely worth ducking in/climbing up.