What's the best way to create a booking form?
If you're new to Drupal, I would first try the webform module.  This is a very popular, well tested module that often gets security fixes which less commonly used modules may not get.

It has all the basic functions you need for creating the options for the form and can easily be configured to send an e-mail upon submission.  It will also leave a record of all submitted data in the Drupal database.

To be honest, off the top of my head I'm not sure if webform can do the computation you request or not.  However, for that there is the computed field module, which will allow you to write a simple function in PHP to compute the value.  Alternately, you could use the rules module's "on node save" event with the action "compute data value" to calculate the total price.

There are a number of other approaches as well but these are commonly used Drupal modules with fairly good documentation and thus are, I think, a good place to start.