Require E-Mail address at the beginning

[BigAndini]

When I start at the order site, no e-mail is required.
This is only required when I want to finish the order.
So far, technically OK, but clumsy.

I think that the most logical would be:

• at the start site, you ask al the required data from the buyer:
  e-mail
  check age (only adults can order?)
  Later, you can specify for whom the ticket will be.
  (the buyer or someone else - here you only need name and date of birth).