Yes, Jean. You ARE being unrealistic. In many areas.
From your description, Ken may be too impaired at this point in his rehab. to benefit from a SD.
I know: that sounds cold.
This is what I understand from your posts and topics in other posts: Ken does not make decisions on his own. Ken is not able to care for himself independently. Ken has an abundance of specialized care givers 24/7 including a spouse.
It is my professional opinion that you are barking up the wrong tree. I believe the best choice is a Companion Dog that will do simple tasks (retreive, come, sit, catch, get it, stay, wait, back, no, drop it, give, pull... all very simple but engaging and useful)
I don't get the feeling that Ken needs more at this point that a pet he can bond with and enjoy the confidence building and therapeutic benefits of feeding, watering, kenneling, walking, playing with dog, and grooming/bathing the dog. He could use a small breed and experience very close and personal interaction with a dog! Maybe even a parrot! Maybe even just a really great cat!
Whose dream of having the SD is it? It sure doesn't seem to be his team! I don't get any feeling from your posts that Ken is the spearhead for this adventure. What are Ken's dreams and wants?
A dog will have a doozy of a time with the varied and transient caregivers. It won't bond with the person whom it is being purchased and trained to do work for. In order for Ken to be safe having/using a SD - they MUST bond very closely. The scenario you describe totally will prevent that from happening. Who will be legally and financially liable for Ken who may become injured (fatal is always a possibility)
as a result of the negligence you are creating while putting a SD in his life?
This situation really begs to be reasessed with more clearly defined goals, plus at least 3 trainers putting in a bid on training. From all you have said, I have no sense the trainer knows what she is doing.
Roxie