Touchscreen is a bit overrated. At the moment, AC isn't very touch-friendly. With mac/apple, you'll need to use some sort of remote desktop application like a Terminal Server or AC in the Cloud.
You can get hybrid touchscreen laptops for cheap nowadays. I've seen the Inspiron 15 hybrid touchscreen for as low as 400. Several practices have requested touchscreens, but most have found it inefficient compared to a regular keyboard/mouse. I have one practice with Ergotron arms and fixed desktops in every exam room. After a while, they didn't use the touch screens at all. They are a good size at 23 inches and have free range of motion. So my advice would be to make sure you find it more efficient than a regular keyboard/mouse.