1.5 days in Paris

Only 1 hour in the Louvre will be tough, you'll want to carefully prioritize.
Yes, using your words, it's easy just to grab something fast somewhere. This is because you have so little time.
It's worth it to do the Seine cruise once the lights come on, there are websites that will tell you what time sunset is.
That's Marais (correct spelling will help you in internet research).
Look at a map and see if Places des Vosges is a place to which you want to walk.

Instead of your river cruise, I would consider getting a 24 hour Batobus pass. This stops at several places on the Seine and circles around, I remember there were stops near Notre Dame, the Louvre and the Eiffel tower. I think the boats ran until at least 9 pm, and it means you can have a trip down the river as many times as you like without committing to a time. Can save some tired feet as well.

If time allows Saturday, consider the archeological site under the plaza (Parvis) in front of Notre Dame, before or after visiting the cathedral. Remains of the Roman town where it all began (pretty much).

After the Eiffel Tower Sunday, how about the military museum at Les Invalides? With Napoleon's tomb as a bonus? And the Rodin sculpture garden nearby if the weather's nice? Or walk across the river from the ET to Trocadero and see the Naval Museum (Musee de la Marine)? Then up Avenue Kleber to the Arc de Triomphe, maybe to the top for another view, and walk down the Champs Elysees toward Place de la Concorde, Tuileries Gardens, and ultimately the Louvre. With frequent stops for rest, coffee, people-watching. If you have the energy, a side-trip from Concorde to the Madeleine would get you to a very different church from Notre-Dame. But you might want to check their Sunday schedule to avoid (or attend) a service.

Perhaps after checkin at your hotel show the boys the crazy 'inside out' architecture of the nearby Pompidou Centre. Ride the escalators in the external glass tubes for unforgetable views. Then on to Notre Dame via Hotel de Ville. Follow this with a walk along the Seine by Pont Neuf and Pont des Arts (former home of the love locks). Return to your hotel via the Louvre courtyard and Rue de Rivoli.
On Sunday after the Eiffel Tower consider a tour of the Paris sewers (Les Egouts) which is nearbly. They may also be interested in the macabre nature of Napoleon's tomb at Invalides, or every boy likes to imitate 'The Thinker' at the Rodin Museum, also nearby. It's a wonderful walk from the Dome Church (Invalides) across Pont Alexandre III past the Grand and Petit Palais to the lower Champs Elysees. Take the metro from FDR stop to Etoile for the Arc de Triomphe. After take the metro back down to Concorde and its a nice walk to Madeleine - Opera - Place Vendome - St Honore - Palais Royal before you arrive at the Louvre.

I totally agree with Dick suggestion that you take the boys to Invalids Army Museum .. perhaps after the Eiffel Tower.. ( if you have timed entry tickets for ET no need to arrive much before your time slot..you will line up in a separate line just for timed slot entry holders and you will be admitted only at time of slot..so don't be more then 10 minutes late for slot or you can look your admission!!)

My two boys ( aged 13, and 14 on their visits) and even my 11 yr old daughter ( they all had one on one visits to Europe with their father or I ,, instead of a family trip with all of us going at once) all said it was one of their favorite museums. Its never crowded.. and the display are usually considered a lot more interesting then "art" at places like Louvre. Don't get me wrong.. two out of three of my kids liked Louvre also( one son hated it.. but he has issues with crowds ) .. Napoleans Apartments were a hit.. as was the Medieval Louvre .. but only my daughter was interested in the painting galleries.

We all agree going to Louvre to see the Mona is a huge let down btw..and I have been enough times that when I visit the Louvre I avoid that gallery !

Thanks for the suggestions - maybe we will slip the Louvre and do the Army Museum instead. My 10 year old said he wanted to go to the Louvre but I think it's just because he has heard of it - were only planning an hour there anyway since their attention span for art is very short. We are doing the Imperial War Museum and Churchill War Rooms in London, and then Anne Frank and Dutch Resistance Museum in Amsterdam - they have been pretty into WWII lately, so maybe we will do better at the Army Museum for that perspective.

Thanks for the help!! :)

Kim

We did not see many children with their parents at the Louvre. There were a few school groups, but most of the school groups were at the Orsay and other Paris art museums where the art would be more interesting to children than the art at the Louvre, which is all pre-1850.

Our first trip to Paris, we had 3 full days, one was planned for Disney Paris since my younger daughter was 11 and we thought she'd be bored just touring the city. The Louvre was the first place she wanted to visit, mostly due to her familiarity with the Mona Lisa, so it was the first place we visited. We went straight to the Mona Lisa, per her request. She enjoyed it and actually wanted to go back.
If it's someplace the kids would like to see, I'd go and check it out for a bit and see the exhibits they are interested in.
In our 3 days in Paris, day 3 we spent in Disney, during our other 2 days we visited Louvre, top of Eiffel Tower, Notre Dame, DOrsay, lunch in Tulieres, Montmartre. We took a boat from Notre Dame to the Eiffel Tower during the day.

Invalid is pretty cool, it starts with medivel weapons, spears ,lances, etc then progresses through muskets, suits of amour, samarui swords, and even horse amour, and then WW l and II. It's nicely laid out, and never crowded, and Napoleons Tomb is right next door.