A touch PC is going to be pretty expensive for that solution... another option might be to split the two -
keep your tablet-orbiter idea for the orbiter but have a low-spec PC or old laptop as the MD sitting under the counter somewhere driving the sound. That's the way I run my kitchen setup and it's very neat and unobtrusive. All you see are the speakers which are pretty discreet and then I just drive the MD and sound from a mobile orbiter (phone, or tablet if you like).
The advantage is you can spend a lot less on what is just a sound station. Disadvantage, of course, is you don't get video or any of that but then you can get all the other apps and whatnot on the tablet.
Another link to follow regarding the mounted/touch-screen stuff is here:http://forum.linuxmce.org/index.php/topic,13004.0.html