While most lots in SF are 25 x 100 there are some areas where the lots area larger in the areas West Of Twin Peaks especially Ingelside Terrace. Many of those homes are on lots that are over 5,000 sq ft.. Many other of the neighborhods in this section of the city are great for kids. West Portal, St Francis Wood, Monterey Heights to mention a few. There are also many natural areas with in walking distance like Mt Davidson, Stern Grove, Golden Gate Heights and of course Golden Gate Park is also close by.