Paris in December is beautifully decorated and New Years Eve under the Eiffel Tower is something you will never forget. That said, it is cold and there is a lot of outdoor walking from metro or bus even if you're only doing indoor attractions. Personally, our favorite time to go is the end of March. They seem to raise plane tix the 1st of April (poisson d'avril!!!!! yummmm, chocolate!) so if you go just before that you'll score a deal. Personal hotel pick: hotel de la bourdonnais, 5 minutes north east of the Eiffel Tower. FWIW, One of my friends who lived in Paris told me that strollers are more easily accomodated on busses and that's what Parisians with small children take. Bonne chance et bon voyage!!!!