We didn't have a 'voucher' either, just email confirmation, but i think all I showed was my driving licence at the exit. I asked about adding dh but they said he was automatically included and we didn't need to do anything, so no need to go to customer services or anything. Dh was driving as we exited, and it was clear that I was sitting in the passenger seat handing her my driving licence as the Gold member, so its not like she mixed us up.....
For return, the lady checked everything and signed us off as having no charges (for fuel etc) before we'd even finished getting our bags out, so I can't see any possibility for dispute doing it that way. Just keep your contract to hand when you give the car back, and then its all done and dusted very quickly.
We didn't have a choice of cars either as there wasn't anything else in our class (or bigger) by the time we picked up. I realised later they'd sent an email which had a link where I could have made a different selection if I'd opened it sooner (its a live link so I couldn't look later to see what we might have had). So if you can, and if its important, check your email as soon as you land. We had a Chevy - it was what they list as their typical Standard SUV. It was fine for us - but our 3 cases completely filled the boot, (hand luggage and buggy had to go on back seat and foot well) so would have caused problems if we'd been a 4 or 5. The car was fine in itself - leather interior, reversing camera, electric boot operation, great condition.
I'd definitely use Hertz again - we paid about £30 more than I could have got Alamo for, and I would pay that differential again for sure.
Hope you have a great trip.
Sencybil xx