Ask HN: Building a website with event calendars, registration, and payment

I need to build out a website with class calendars and the ability to register for different 1 time classes, with the ability to allow the user to pay on line and get them registered for the class. Should I use something like paypal or braintreepayments?

This isn't a 1 time event, but basically an ongoing calendar that people can register for different days/times. Anyone have any tips of suggestions?