Good for you getting a horse from CANTER! I adopted my OTTB from CANTER and support their efforts to help retiring racers find new jobs.
Remember: what you see when you see a nearly retired racer, especially the ones on CANTER, is often one that isnt feeling too good. They are generally underweight and over-raced, and not happy being in stalls 23 hours a day. You will find that you have a very different horse in a couple months, and in a year, you won't believe the difference.
I find it curious that if a horse is winning on grass, why they would want to retire it. That is odd, unless there has been some kind of injury. Did you read the report of her last race?
Number two looks scrawny now, but with the right diet, top line work, and TLC, has a lot of potential. If she is ponying horses, that is an excellent sign about her abilities.
Someone should report the owner of #3 for neglect. I cannot believe how bad her feet look. Seriously, you may want to let the track vet know.
You cant' go wrong with #1 or #2 in my opinion. Good luck and let us know what you decide!