They are very cute puppies, but as an owner of five Purebreed Yorkies, I must say
SHAME ON YOU
Continuing to breed for an outcome of mixed breed dogs makes no sense.
You are in no way bettering the breed or line but you are adding to the overpopulation of mixed breeds, many of which end up at the pound. 
It's nice that you want to provide a puppy for disabled people. May I suggest that you get them a gift certificate to the local humane society so that they can give a puppy that
is already here, a good loving home. A $100.00 girt certificate is alot cheaper than the $250.00 you say you will sell them for to recoup your costs.
