I don't like to make recommendations for whether or not other people should buy from someone else, but there is plenty of information about the conditions of these snakes for you to make an educated and informed decision. I know that some of these snakes can be saved with proper treatment, and Kitkat has actually gotten lucky and not noticed any ill effects at all. You should also factor in the cost of vet bills (
Vet Bills) before making a decision. To give them the best chance of surviving, I'd take the snake(s) and the first fecal sample(s) to a vet right away for diagnosis and treatment. Only you can weigh the impact that a dead snake would have on your 12-year old.
On the other hand, I've been in contact with Scott Felzer, and he's bred and is expecting at least one litter of these blue snakes in about 1.5 months. He's selling the babies for $40 each. Hope this has been helpful.
Rick