From personal experience - unless you actually need a virtual whiteboard... large format touchscreens are USELESS.
I've used a 60+ inch touchscreen, and it's just ludicrous. Despite being full-HD res, you are so close to it to touch it, that you can see every single pixel looking right back at you. It's also exhausting to reach to the corners of the screen.
Any touchscreen over about 24 inches is just silly.
Might I suggest a smaller touch-screen machine, hooked up to a projector that's mirroring its display?