We stayed in the apartment at the end of October as a group of five including our three children (ages 6, 4 and 1).
The apartment is very well suited for children with a thoughtfully decorated children's room with bunk beds and a selection of toys that were very much appreciated on our visit. We self-catered for much of our stay and found the kitchen well equipped with everything we needed. There is a high chair and baby bath for very small children which came in useful. Near to the apartment is a small supermarket which is perfectly adequate for a short stay and had everything we needed. The apartment was fully kitted with appliances including washing machine, dishwasher TV and even a Playstation 4. There is both heating and air conditioning dependent on the time of year.
The location is near to Atocha station which we found to be a quiet neighbourhood within very easy walk of two metro stations to reach other parts of Madrid. We were able to walk to the main sights although some we found it easier to use the public transport system. Airport access is very easy on public transport from Atocha or by Taxi. The apartment is on level 3 with lift access for luggage and in our case a pushchair.
We were met for the check in at the apartment which was extremely helpful as the host provided a tour and explained everything we needed to know. We were provided with fruit and muffins on arrival which was a really nice touch. We didn't need to contact the host during our stay but had asked a couple of questions ahead and received a quick response in all cases.
Overall we had a great trip to Madrid and found the apartment experience much more relaxing that a hotel would have been for our family. We would highly recommend this accommodation, especially for those travelling with small children.