You will need a big antenna mounted above the roof not in attic pointed at 315 magnetic compass reading. The Winegard HD7698P . . on a tripod mount or eave mount . No cheap flimsy eve mount , this is a big antenna.
http://www.solidsignal.com . Yes you can use the coax wiring that is in place now. Connect one Tv to begin with coax going from the antenna to the Tv , No Splitters. See how many channels can get. Then connect up the other Tv's with a splitter , the signal level will drop. If many of the signal levels of the channels drop down so low that the Tv's can not lock on then add a pre- amp signal amplifier , I suggest a winegard AP8257. Keep the antenna at a height on the roof that you can mount the antenna while reaching up a little , no need to do any monkey swinging - death defying manuvers , two or three extra feet up beyond your reach will not get any more signal. Here is a great way to keep the coax from swinging in the breeze , feed the coax up through the bottom inside the antenna mounting pipe and out the top of the pipe and connect to the antenna. . A channel master cm9030 eave mount or can even use a cm 9067 chimney mount.