Outputting live means that GoPro is out, as the latency is quite high. The distances are also right on the limit of wifi in any case.
Best bet would be CCTV cameras with digital video outputs - SDI, linked to an SDI switcher. HDMI would be better and would allow you to use domestic camcorders, but more costly in terms of switching - see below, and cable lengths are limited to 30 - 50M unless you use fibre or Cat6 distribution
To avoid roll and in the case of Digital SDI or HDMI, blank screen on switching, you will need a synchronous switcher, which re-clocks the signals so that they are all frame accurate. This usually means a video mixer - or switcher with built in TBCs. Alternatively, you sync the cameras with a 2nd cable running from a SPG to each camera and use a Vertical Interval switcher or matrix. This is now quite old tech, but was the broadcast way until about 10 years ago when everything went digital.
Analogue video is good for 100M - 1000M depending on cable, while SDI will do a similar distance. Joins and poor quality cable make the biggest difference to the signal. Impedance is very important and connections must be made correctly using the correct impedance connectors.
So, you will need cameras, high quality cable, possibly line isolators in case of mains earth loops, a switcher or mixer and then distribution back out to the TVs.
For composite video resolution, Panasonic MX50 video mixers are now reasonably cheap, but Roland V-Series are very good as well. Their latest models take composite and HDMI, so you have an upgrade path. Don't forget some preview monitors so you can see the feeds. Quad splitters allow 4 signals to be displayed on 1 screen - often a simple VGA PC monitor.
SDI equipment is now quite cheap, as it has come out of broadcast installations and is now commercially worthless. A mixer with built in TBCs - Snell and Wilcox Magic DaVE can be picked up for £200 or so. The CCTV cameras are a few hundred each, plus a suitable lens for each. Use PTV and a pan and tilt head and you can have joystick control of each camera as well