We had a good stay at this apartment. It was clean and had everything we needed. It is probably a bit small to comfortably hang out in for a family with 2 teens but there is plenty to do in the area so not a big deal.
It is in a great location, only short way away from the center of Cottesloe and Cottesloe beach ... We enjoyed trying different Restaurants, Pubs and bars every night. Be aware a lot of them require bookings as it is a very busy area.
Only downside was the neighbour above who had TV going extremely loud all night. (Had the fan going the after the first night which drowned the noise out and the kids seemed to cope.)