Finding a program to automate my bookings

I am setting up the website for my business. On the site I sell 6, 12 and 24 week packages of weekly children’s shows. I am trying to find a program that will automate my bookings so that once someone makes a booking it goes into the system, I can bring up their information easily and take payment from them in person, if the show is full it will automatically tell the person booking to choose another day or go or the waiting list. What program/platform do you recommend?