Simple order form integrated Authorize.net

We have a site that people come to register at for our seminar. We do not want to use a shopping cart to have them register. Shopping carts require too much time and work. We have seminars in several different cities. The people that come to our site will need to: 1. Choose the date/city they want to attend. 2. Enter a quantity for the number of people attending. I want it to calculate a total before they checkout. I want a simple form that does not require multiple screens to complete. In one form they should be able to enter the name, billing address, etc., credit card info and hit Submit. The form will need to be integrated with our [login to view URL] account and then take them to a receipt page when they are done, or an error page if there are problems.