Paris
L'amour
You're going to have to take your kids to Paris at some point. But you should go there without them if you can. Paris is for love, after all.
Art and Architecture
Your kid may be precocious and wise beyond his or her years, but really, there's only so much high art they'll tolerate. You, as an adult, could spend hours and hours in the D'Orsay alone. Give your self a chance to see all the things you want to before having to bend your schedule to a cranky kid.
City of Lights
Or, skip the day sights and head out at night. Linger over a long dinner, catch a show of any description -- they run from "important" to low-brow -- or wander around the beautiful night-life neighborhoods.