We stayed at the apartment with our 1.5 years old son, and it is a great fit for children! It has all you need for a child - baby cot, a small bath, high chair, toys. Also the apartment is child-proof, for example all power sockets are covered. Apartment has great amenities: gas oven, coffee machine, good selection of cutlery and dishes, and many other things.
Apart from that, the apartment is located just across the road from El Retiro park, which is perfect for walking with kids. Also there are many other sights in walking distance: Prado museum, Reina Sofia, Botanic Gardens. Public transport - metro, train station, bus stop - everything in a walking distance too.
That's a great apartment to stay, highly recommended!