I have arranged general help for my elderly father-in-law, who had both poor mobility issues and general unease about navigating airports/connection. I requested the assistance over the phone with AC reservations - no problems at all, and father-in-law reported courteous and effective assistance from staff at the airport. If I recall correctly, I just told them he required wheelchair transfer between gates and general assistance (e.g. boarding passes, communicating with gate agents boarding, etc).
These were short domestic segments though - I'm sure others can comment on the potential challenges of getting assistance with connections involving non-AC staff at international airports.