Go for it with the Turkish, Q! I have a dear friend who came from Turkey, and I think it's a great language. I've considered having my kids take it, but DH argues that it isn't "useful" enough. I like the "niche marketing" aspect though- I think it might make a person more interesting and valuable to employers later. It seems like everyone is learning Japanese or Chinese these days.

Any second language will be good for him, and make it easier to acquire others.