Yves place is in a great location, steps away from the Jardin de Luxembourg. We traveled with two children (10 and 3 yrs old) and the playground in the garden was great. The apartment is also steps away from the RER B metro and in the heart of the Latin quarter. It's within walking distance of many sites including Notre Damn cathedral.
The apartment itself had some downsides. First, there is no elevator. We knew this from the beginning and we didn't think it was a problem climbing the stairs. Second, there is no air conditioning. We didn't realize there was no air conditioning and it was really hot in Paris this past week. After we climbed up with all of our bags and our kids, we realized there was no a/c. The apartment itself was fine. I think it had ample room for all of us. The kitchen was well equipped, although we never used it. The furnishings were clearly rental quality with broken light fixtures and a ripped tablecloth. The bathroom only has a tub with a shower wand. Overall the apartment was fine although don't expect much in terms of high quality furnishings.
The apartment has large windows and a small balcony overlooking the road. The railings don't go to the bottom of the window. Our 3 yr old son almost fell out of the window as he tried to crawl under the iron railings. I was worried all the time we were in the apartment that he would fall out of the window and had them closed all of the time. And it was hot. There is also an older lady who lives in the apartment underneath this one and we were asked to not run and keep the noise level down as to not disturb her. We tried to keep our son from running and stomping as much as possible, but he is a 3 yr old. I would just say that if you are a parent with young children, this apartment is really not suitable to children.