@sbtheplumber1
All good questions, let me see if I can answer some.

Most hotels have Mayo discount, you do not have to show any proof, call hotel directly to make reservations to get the Mayo discount.

Mayo wheelchairs are free to use. Not sure if can take offsite, but I see people using in downtown area and can take to parking ramps. That would be good question for Mayo consigner service. Also, they have Mayo employees who are called "transporters", use to be called escorts. If your son is not with you, and you need someone to push the wheelchair, they will get you from entrance to your appointment desk. Just ask the door attendant.

Access to Gonda for evening appointments: On portal under appointments, there is a link to "Patient Appointment Guide", this has additional instructions for appointments. It should have instructions on how to enter building for evening appointments. I had a imaging exam years ago later in day and had to enter via Charlton Building entrance and then go to Gonda building via a locked door. There was speaker button to talk to security that then opened door remotely. All the instructions were in my appointment guide.

There are multiple parking ramps close to Mayo, they do charge. There is also a valet service for an additional charge. You can also drop someone off and then park car if your son is driving. WARNING - the drop off area at Gonda can be very busy, especially in morning, so plan extra time if using valet or dropping someone off.
https://www.mayoclinic.org/patient-visitor-guide/minnesota/parking
Alos, parking on streets around Mayo is free after 5 PM.

Keep asking question, Mayo Connect members have lots of experience with logistics of navigating Mayo. It can be overwhelming for first appointment, but there is always people to ask.