As a guitarist, I would have to say that if you have to choose amongst those instruments, a guitar backup for fiddle and whistle (I like whistleist!)would be best for the sound, but I can imagine a bass behind fiddle/whistle would be a neat, if different, kind of sound. Or, for that matter, chorded banjo. If you can give the caller and dancers what they want, they'll accept a unique sound. For awhile we had 2 flutes playing with us and we loved it.

One cautionary note: if you break a string in the middle of the tune and you're playing guitar, don't stop! I did once and the whole thing came crashing down on me. I hadn't realized how reliant they were on the rhythm.

If playing jigs comes easy to you, that's a great talent. I've got only a drop of Irish in me- maybe I need more!