Bett I have heard the cruise can be a bit of a snooze fest.. too long very slow, .. and there will be no Parisiens on it( why would they bother.. they would walk or take the metro , not a 2.5 hour canal cruise !) I do understand you want to find something a bit unique to do.. perhaps a tad off the beaten path..
I have heard good things about the Calife dinner cruises.. google for the webiste I like that its on a cute older type boat and not the giant sightseeing type ones. I am going to try it this year myself after reading many good things about it. Once again,, doubt many locals would bother with it either.
Bett.. I have relatives in Paris.. they simply are not doing what most tourists want to do all day.. they work, they go to doctors appts.. they do laundry , shop for food, take out the garbage and pick their kids up for school.. I think people have some fantasy that all the Parisiens do is drink little coffees and paint. .lol no , they are just like you and me at home!! So enjoy being a tourist.. we are lucky , we can sightsee all day long.. take long coffee breaks , people watch.. wander in parks for hours.. enjoy being a visitor!!
Perhaps you would enjoy exploring some different less central areas of Paris this time around.. many enjoy strolling through the Parc Des Buttes Chaumont ,, its very pretty and there will be some locals enjoying that park! google for some images!