Canal Saint Martin

There are others who are more experienced, but I would not spend four nights in that area. The canal boat ride is slow, slow, slow - not that interesting, in my opinion. I would visit the area for a day, but that's all. There are so many wonderful areas in Paris. I'm sure others will chime in with suggestions.

Rick's guides are not comprehensive. He reviews the obvious and places he enjoys. I suggest supplementing his suggestions with one or more guidebooks or websites and build an itinerary based on your interests.

Stayed just off the canal for 5 nights several years ago and enjoyed it. Many good restaurants in the area.
Stayed at the Belta Hotel, there is also a Timhotel nearby.
Loved Les Enfants Perdus. Chez Prune is nearby and highly rated, but did not eat there.
Canal Saint Martin is a nice place to stroll, but I would not bother with the boat rides.

Area is fine to stay but I agree with the other Janet that the canal boat trip is like watching paint dry. -- it is fun to watch the boats go through the canal once or twice with the interesting swing bridges. We also meet friends along the canal for Apero on Friday nights. There are picnic tables right on the canal here and there and nearby cafes will bring drinks and snacks.

Stayed not too far from there, Citadines République. Decent apart-hotel though rather charmless. Overall the area is a good one for just chilling and enjoying Paris, rather than sightseeing.

The full canal boat ride takes hours because you have to go through four sets of locks. So slow! I believe there is an abbreviated version that skips all but one set of locks (heads downstream to the Seine rather than from the Seine all the way to Bassin de la Villette), and I would consider taking it because the section under Boul. Richard Lenoir is pretty wonderful to see IMO.

We stayed in the Canal St. Martin area for four days in the first week of July.
We chose it because it was a little less expensive and at a time when not as many accommodations in Paris were available.
It’s a nice neighborhood but not a hub of attractions.
If you want to minimize walking or transportation time you may prefer to stay closer to what you’d like to do. However places in the 4th, 6th and 7th may be more crowded and more expensive. We got used to the Metro early on our first Paris trip and use it as our primary transportation. You do have to be able to navigate steps for some of the stops. So far we are still able to negotiate them.
We stayed at the Hotel St. Martin Bastille. The Bastille market is held across the street from the hotel on Thursdays and Sundays. It’s a functioning market for people in the neighborhood so most people are there doing their shopping for groceries but there are some clothing items as well. We didn’t take the boat but we enjoyed walking along the canal and watching the boats and stopping for a drink along the way.
We ate at four restaurants in the area and liked all of them. Our favorite was L’Officine/La Pharmacie. It recently changed its name and I don’t think all the signage has changed. Very nice meal and our server was excellent at suggesting some great bottles of wine that didn’t break the bank. We celebrated my sister-in-law’s birthday at L’Angelus dû Canal. It’s a small place and the guy who is seems to be the manager couldn’t have been more charming. Astier has been around a long time. We had a memorable meal there 35 years ago on our first trip to Paris. It’s aged well, food and service were both good. L’Ange 20 is small like L’Angelus dû Canal but we were treated very well here. It was probably my least favorite of the four but still good. I would strongly recommend making reservations for dinner. At least three of them could be booked online.
As far as points of interest I would suggest the Orsay museum for impressionists if you haven’t been and the Orangerie museum which is basically Monet’s Waterlillies but would be nice if you’re going to Givery where he painted them. Also, if you have any interest in WWI and WWII, Invalides has a great museum that takes you from the beginning of WWI to the end of WWII. They also have Napoleon’s Tomb.
Good luck.