You have a good idea on using mobile application. It will not only give convenience to the customers on how to order thru the mobile phone, but give some information about coffee, caffeine, and its health benefits. There might be some problems encountered by a barista if the orders are done simultaneous and how long does a customer can wait for the order. A thorough study and coding should be done at least to minimize some problems at the start of the application.
John has the right approach. The mobile app could work but it seems like it's trying to solve a problem that is caused by the proprietors themselves. In fact, there is a nebulous, possibly large potential customer base that exists between the extremes (dunkin lovers vs woodneck cloth filter snobs). Proprietors need to be the educators; the catalysts to knowledge and understanding. Who is going to take the dunkin lovers and turn them into snobs? The dunkin lovers, for the most part, aren't going to go out of their way to educate themselves. It's kinda the sign of the times. Creating a simplified, direct, focused menu with explanations for different drinks goes a long way to converting casual customers into aficionados.