I want to get some feedback re: various string instruments and playing Irish "diddly" music...

I am not looking to play guitar (simply because I want to play something different). I was thinking of instruments preferably tuned like the Irish tenor banjo: G-D-A-E (Now if the tuning is the same between instruments, is the fingering also?)

Instruments that come to mind:

Octave mandolin
Mandolin (though I know the tuning is different)
Mandola
Banjo Mandolin (don't know how these are tuned)
Other suggestions?

Here's another thought...if the 5th string is removed from a G-banjo, can that be strung and tuned like an Irish tenor banjo and learn the fingerings that way until I might get a tenor or other G-D-A-E tuned instrument??

I've been a woodwind player most of my life, and now I want to expand my horizons...thus, I know not much about the above instruments. So any feedback (and joking) will be much appreciated.

Thanks,

Mary