I frequently receive day of schedules which contain something along the following lines as far as the timing of the cake cutting goes.
8:45-8:50 First Dance
8:50-9:00 Parent Dances
9:30-9:40 Cake Cutting
Having seen this order of events play out countless times, I now think that maybe it's not the best idea to "break" for cake cutting so quickly after open dancing begins. The above time frame can be confusing to guests and may have a deflating effect on the energy of the dance floor.
Over the years, I've noticed that something happens to the party atmosphere during that time. Frequently, return to the dance floor, they are not as enthused as they originally were when open dancing started.
A much better option is to perhaps do the following: eat dinner, followed by toasts, first dance and parents dances and immediately after that, cut the cake. This way everyone can enjoy the cake and have some coffee all before they jump on the dance floor!