This flat suited our family (my wife and two 10 year olds) very well. It is in the pedestrian blocks of Gracia and is conveniently located to all means of public transportation. We used the bus and the metro to travel to Camp Nou, the Barri Gotic, et cetera without problem. The flat itself is on the 3rd floor and is situated in the rear of the building, away from any street noise. The a/c is fantastic. There are plenty of supermercados, cafes, all within walking distance, that provide easy access at the end of the day when perhaps everyone is too tired to make it out for dinner. 10 minute walk to Passeig de Gracia for dinner and shopping. I recommend this flat if you are looking for a stay that is away from the bustle of the center of Barcelona but still conveniently located, and looking for a place that provides enough space for the family to stretch out.
TIP: We had a rental car that we returned before traveling to the apartment. As mentioned above the streets are drivable but largely pedestrian traffic. I'd recommend returning your car before arriving. We were there during Gracia Festa when many of the streets are shutdown for the weeklong party.