Don't hesitate to book that apartment.
That is an ideal place for staying with children. We were two families with three children (1y5m, 1y7m, 6y). Filip can get everything you need.
Filip is a super-host: intelligent, polite, calm and quick.
The flat is spacious, clean and comfortable.
The location is outstanding. On the one hand, the neighborhood is calm and peaceful. There are three supermarkets, couple children's playgrounds, lots of restaurants, cafes and pubs without tons of tourists.
On the other hand, you can reach Prague's sightseeing attractions with streets stuffed with tourists in several minutes, even on foot, even with children.