I stayed here with my nearly four year old and it was perfect.
I know Paris extremely well, so maybe the area isn’t for everyone, but it’s super close to Gare du Nord and had all amenities you need for a four year old: park, bakery, supermarket, pizza place, pharmacy, metro close by. There’s also a mini-city farm with goats if you head in the Gare de l’est direction. We live in Harlesden in London so it was home from home for us (minus the goats).
As with most Paris flats the space is compact, but literally everything was covered (especially dishwasher, loads of catering equipment and washing machine). There are two double bed so I was able to sleep separately.
Two things (if sharing and with kids) to bare in mind: there’s only a curtain between the two spaces, so I did a lot of creeping around to torchlight wearing headphones once my son was falling asleep, and it’s only got a shower. Neither of these caused us any inconvenience and the stay was just perfect.
Ludivine was super helpful, and left a Peppa Pig in Paris book - which my son loved and quoted from at the top of the Eiffel Tower (“look - the people look like ants”). It’s still there for the next people!