Buy yourself the most expensive Melodeon you can afford. Then you will only have to carry it around to be universally accepted by Morris Teams Session players etc. without ever learning a note.
The melodeon is the last refuge of the musically incompetent.
However, if you really do want to play an instrument, get a five string banjo. Its open G tuning lets you play loads of tunes very easily, and its very easy to develop your own style. As to not wanting to dance - well thats another issue - why not Learn to dance its easier than playing -believe me. Its no fun after a four hour stint with a heavy instrument around your kneck - its definitley easier to learn a few basic dance steps.