Since your time at the Louvre would be limited, you could
also do a self-guided tour (renting the headsets) that includes the highlights.

Two hours will be enough in both museums. However, the Musee d'Orsay will be undergoing renovations so the Impressionist paintings will not be on the 5th floor. The collection is definitely worth seeing.

If you have to skip anything make it the Champs walk.

I love Notre Dame, it wouldn't take long to visit and the kids would enjoy climbing for the views and photo op. Look for the "Point Zero" marker in the cobblestoned square in front of Notre Dame. It's on the right if you are looking at the front of the cathedral.

"Kilometre Zero of French national highways, located in Paris on the square facing the main entrance of Notre Dame cathedral, and considered the official centre of the city of Paris."

Definitely walk along Ile St Louis and enjoy some Amorino gelato. There are benches along the Seine, so you can take a break there.

If you're concerned about getting tired, take a bus or metro from the Orsay to the Eiffel Tower -- or vice versa.

Have a wonderful time on your cruise and in Paris

One of the best views of Paris is from the casual buffet type cafeteria outdoors at the top of the Galerie Printemps department store. (Lafayette next door)It is 360 degrees, very reasonable prices, good for kids. Shopping is amazing, as is food court in Lafayette.