It's a great use case and one I see all the time.
This is going to sound like a shameless plug, but *a tablet* app handles visitor and contractor registrations, and integrates into ClearPass for automatic creation of the guest accout.
**Removed Shamless Plug Link** :)
It's such a good feeling when you visit a place with a great visitor system with guest wireless. There are a number of visitor systems like this, and the more you automate, the more consistent and easier life becomes!
Cheers
Grocke
*Edited as the more I look there are lots of integration partners and I don't want to prefer one above another*