I'll third or fourth or whatever the trike Idea. A good trike is going to be rather more expensive than those electras that you are looking at though. But if memory serves they make greenspeed trikes there in Australia, and they are supposedly they are the best trikes they make. If I recall Sheldon Brown was rather fond of his... <sniffle>
As far as the electras models go I would stay away from the one with the roller-brake, they don't have the stopping power for a normal rider much less an Athena. Also with the V-Brakes by adjusting (possibly changing the levers) you can adjust them so that they have enormous stopping power with very little travel and force on the levers. Overall as bikes go they are really nice bikes, I'm looking at one of the single speed coaster brake models for my mom who has very sever Rheumatoid + osteo arthritis and Fibromyalgia.
Out of curiosity what medication were they able to put you on?