Places to go with the Kids
A couple of hands-on kids museums/expos/science fun...
http://www.cite-sciences.fr/francais/ala_cite/expositions/cite-des-enfants/

Reduced Tickets for shows, including kid stuff...
http://www.billetreduc.com/

Go swimming! Most pools have an area for kids that isn't very deep...
http://www.paris.fr/portail/Sport/Portal.lut?page_id=8409

Jardin d'acclimatation...
http://www.jardindacclimatation.fr/

Visit the fish at the Aquarium...
http://www.cineaqua.com/

Good in summer- the themed gardens in parc de la villette...
http://www.villette.com/fr/parc-villette-jardins/

Forum des images by les halles, it has really good films for the little ones and it is also good there without kids...
http://www.forumdesimages.fr/

If you are interested in joining classes at any topic, the mairie paris offers a lot of them, cheap and good, from cooking lessons to art lessons, they have everything
http://www.cours-municipal-d-adultes-cma.cma-paris.org/

Disneyland! Great for kids and adults alike
www.disneylandparis.fr