Can you think of songs that mention "mandolin" but do not use mandolin on the recording? I can think of 2 or 3.
1. Wild Is The Wind by David Bowie
2. Mandolin Wind - Bruce Hornsby
3. "went to Staten Island to buy a mandolin.." by Joni Mitchell - I can't remember the title.
I think it would be more cool to actually use the instrument that you mention in the song.