Last August we took our 3 grandchildren, ages 6, 10, and 18, and their mother to Paris for 10 days. We stayed in an apartment on Rue des Petits Carreaux, close to a Metro stop and adjacent to a Pedestrian Mall. We ate breakfast in the apt. every morning, often consisting of food we purchased from shops below. We also ate many dinners in the apt; We didn't cook, but bought take out food from the food places on our street: Rotisserie chicken, salads, etc. Lunch was the only meal we consistently ate out every day.
One of the best decisions I made was to book a bike tour for all 6 of us from Bike About Tours (discount in RS book) for a Sunday morning, when traffic is lighter. The 6 year old knows how to ride a bike, but he isn't street-smart, so he rode a tag-along with his mother. It was at the beginning of the trip, so we all appreciated getting a sense of the location of sights in Paris. We also bought discounted boat tickets through them at the end of the tour, and the kids really enjoyed that.
The 6 year old especially loved climbing Notre Dame, Arc d' Triumph, and he even wanted to climb Sacre-Coeur, but it was closed by the time we got there.
We bought Museum Passes (6 and 10 year old free), so we could return to sights, or leave after a few minutes.
Of special interest to them: Army Museum's armor room, as well as Napoleon's horse (stuffed). They even appreciated the Louvre and seeing Mona Lisa.
We rode the Metro whenever possible, to conserve energy for other activities.
We walked from the Louvre to the Arc d' Triumphe, with a stop at Laduree as enticement.
It was a very memorable trip for all.
Carol