To take an analogy - if I'm doing a storytelling booking, because I have a wide range of possible stories I generally ask the organiser what kind of stories they would prefer (ie Greek myths, King Arthur, Welsh folk tales etc) and certainly have no problem with the organiser telling me what they have in mind. I've also had people make requests well ahead of a gig to ensure that certain songs are included in a concert booking - and that's a whole lot better than being asked on the spot to do something I haven't rehearsed or thought of for a few years. Then there are the themed nights or festival events when the task is finding the "right" songs to sing .. specifying an origin for songs is surely only another way of looking at this?
So I don't, personally, have any problem with an organiser asking specifically for a range of my material - in fact, I think it's quite a good challenge to sift through to find songs to fit. Isn't it a compliment, that this organiser knows your repertoire is wide enough to make these choices?

Enjoyed our mini session in Ballydehob, incidentally - we'll have to do it again some time, minus the picturesque drunks!

Anne