We stayed at Eleonore's apartment for 1 week with our 9 month old baby. The apartment is fantastic - there is lots of space, both bedrooms are a reasonable size (the bigger one fit a portacot) and the kitchen was big enough to self cater.
It is definitely within walking distance to the heart of Le Marais. There is a bus and train at the doorstep, but they are not very helpful routes!! It is a short walk to more buses though.
The street has lots of supermarkets, pharmacies and good bakeries (Hure is delicious!!).
Definitely a good option, especially with a family.