Recently I got a Dell Venue 8 Pro, basically an 8" tablet that runs the Desktop version of Windows 8 so no physical keyboard or mouse. Has anyone played any of the DK's on such a setup? Or even on a Windows 8 tablet with a Bluetooth keyboard and mouse?

Haven't tried this configuration myself, but Windows 8 is officially supported. Also the game seems to run best on a low resolution of 640x480 so the limited resolution of tablets shouldn't be a problem and I can't see why Bluetooth keyboard and mouse wouldn't work. The only problem might be performance, as older games sometimes need surprisingly high processing power. You'll have to check that first hand. In the end there's always GOG's 30-day money-back guarantee if you can't get it running.

Minimum system requirements for Dungeon Keeper 1 +2 according to GOG: 1.8 GHz Processor, 512MB RAM (1 GB recommended), 3D graphics card compatible with DirectX 7 (compatible with DirectX 9 recommended), 2GB HDD, Mouse, Keyboard.