With parents and in-laws with mobility issues, this has been my experience traveling with them on DL.
I always book the service when booking their tickets.

At check in the requested wheelchair service will be called.

The attendant will fold up the walker and pull that and carryon rollers to the gate.
Usually one attendant takes them as far as flight security. Once they pass security a different attendant will take them to gate/SkyClub with a different wheelchair.
Depending on them, they can be wheeled to the aircraft door during pre-boarding.
Walkers are always pink tagged and available once off the plane.
At arrival airport they will be met at the plane's door on the jetbridge by the attend at holding tablets with their names on it.
Some airport electric golf carts are used.

They will wheel them to Skyclub and later from Skyclub to gate/plane.

In US and Canada a tip is appreciated.