if it's for kids, and you wanted to try an day/afternoon first Fish creek park has a few easy single tracks in it. as well as the pave and dirt paths. From 37th by the reserve to Secomie(SP?) lake is ~10km
gives easy pick up and drop off points too... if its more advanced stuff or you just want to get into the mountains more, yeah Bragg Creek for sure, I still haven't explored nearly enough out there.