@Gene900 I assume that the room will accommodate the longer beds without looking too cramped. If your ideal guests are families with young children, then regular twin bed sizes should be fine. If you think that you will attract groups with single adults who would benefit from the longer beds, then you may wish to go with the twin XL.
(Be sure to have spare XL sheets on hand should you need to replace damaged sheets -- I don't know how easy it is to get the longer sheets.)
Best wishes for lots of bookings!