Looks like a fine neighborhood as long as you don't mind hilly terrain. Sacre-Coeur may be three minutes away but it's uphill. You'll be between two Metro stations, Lamarck-Caulaincourt on line 12 and Chateau Rouge on line 4, either of which will get you into the heart of sightseeing Paris in a few minutes.
I agree with Andrea, it would be good to ask why no reviews are posted. Maybe because the place hasn't been on airbnb that long. Not necessarily a red flag. Note that it's on the first floor, which means the second, and no mention of an elevator. Also unclear how big the bed is, perhaps only what we'd consider a "full" or "double," vs. a queen. Might be a little tight for your family and 4-year-old. Still the price is good and the neighborhood looks fine, and with your French you'll get much more out of your surroundings than most of us do.
Airbnb doesn't pay the owner till you've been there over one night, so if it's not as advertised you can let them know and you're protected. At least that's their business model, I haven't tested it because our experience has been good. Have a wonderful trip and surprise all the French people with your fluency!