collieflowerr

To clarify OP's point, any dog can detect low/high blood sugar so long as they've been trained to do so. Sometimes the dogs will even be inadvertently trained to alert before a low or high. Not sure why they specifically chose Papillons.

Depending on what you need in a service dog definitely decides what is available to you. For example, I go to a college that primarily trains mobility assistance dogs, but also does a few programs specifically geared towards veterans. They also tend to place dogs that don't have a personality fit for working with a quadriplegic or paraplegic as PTSD service dogs. My university does not charge veterans at all for service dogs.

Basically, look at options available to you and organizations that train dogs that are suitable for your son's needs. Be warned though, a lot of organizations have a verrrrrry long waiting list.

Not sure if you are located near any, but the majority of guide dog organizations don't use doodles. I volunteered at the Leader Dogs for the Blind campus for a year, they definitely do not use them. I believe Guide Dogs doesn't use them either. Canine Companions for Independence doesn't use doodles afaik. Bergin University of Canine Studies brought in a doodle, but I'm not sure if they're going to use her for breeding since they were just testing the mix. And Good Dog! Autism Companions does not use doodles. CCI, BUCS and GDAC are service dog organizations.

Are you against all mixed breeding? Because golden/lab crosses are very common in the service and guide dog industries.

Edit: Not trying to attack you, I know of organizations that don't do doodles, but I'm trying to think of any that only use purebreds. I know of one purebred poodle organization.