Paris is great. Our 7yo daughter loved it too.
We found the tourist bus a good way to get around and see the sights. The Metro is also very good, but watch out for pick pockets (we caught a couple trying to rob some Japanese tourists).
See the Eiffel tower lit up and sparkling at 10pm.
Take a ride on the Seine.
Take a bike tour or take a segway tour (done it in San Francisco, but same company).
Climb up to Sacré-Cœur
Take a walk through the parks.
See the Louvre, just to visit the pyramid if nothing else. BTW it’s not all old paintings.
The Musee D’Orsay is worth a look (arrive early).
Take a roof top tour of the Pantheon.
Printemps (just to see the dome, if not interested in the shopping)
For food we always recommend L’Affriolé on Rue Malar. Not cheap, but quite possibly the most amazing meal I have eaten anywhere.
The list goes on. You’ll have a great time. We found TripAdvisor to be a good resource.