Water: assume none. The Forest Service page and recreation.gov contradict each other on drinking water here, so bring everything you plan to drink.
Granite Flat sits low in American Fork Canyon, which means you get big Timpanogos country without the drive up to the Alpine Loop's tight switchbacks. Roads and parking spurs are paved, and there are three group sites alongside the family loops, so it handles a reunion better than most Wasatch camps. Some sites are held as first come, first served. Plan on vault toilets and no hookups, and keep your rig under 30 feet since SR 92 is narrow.
Tip: Fee canyon. Combo it with Timpanogos Cave National Monument.
Out the tent door: Mount Timpanogos (Timpooneke) (Hike, 4 mi) · American Fork Creek (Fishing, 6 mi) · Cecret Lake (Hike, 7 mi) · Stewart Falls (Hike, 7 mi)