If they're willing to buy, good for you. Internet radio isn't governed by the FCC, since it's not really radio. You could also spell out a certain 4-letter word as your top-of-hour ID and there ain't a thing the gov't could do about it. Since you're not really on the "air" you can swear, make up your own call letters, whatever.
However, after thinking about this for a few more seconds, there may be laws regarding cigarette ads online -- just not the FCC's laws. If you go to any cigarette company's website (booze companies too), they make you "attest" to the fact you're 18 or 21. I'm just not sure if these are mandated or if the companies are just trying to give people some lame impression they "care" about keeping kids out of their sites. Tried Googling it, couldn't find anything.
Anyway, just thinking -- if those birthdate "verification" pages ARE mandated, then you may need to put one on your own site, so users can attest to being old enough before they can listen to your audio stream. Might be something you need to check with a lawyer, or at least some kind of "advocate" organization that offers professional advice on these kinds of matters.