I am making a cupcake tower with a lady in a poodle skirt on top and all the cupcakes will look like 45s.
Any ideas of how i can do this?
How do I get grooves on the cupcakes. should i use a piece of fondant or do it all in butter cream?
the customer is afraid of black icing "tinting everyone's mouth" (is that actually a possibility?)

Yes it certainly is possible to make every smile black!
If you use choco icing as a base then tint it black it won't be near a problem.
I suggest you use fondant that you 'score' w/a fork or clean comb. Other wise there is a tip that has very fine 'teeth' cut (similar to a star tip)...I'm not sure of the # think it is 63 (maybe 99 or 199?). Just pipe b'cream in circles around the top of the cc.