My son and daughter in law both work at a non-profit facility in Georgia that trains service dogs, including seizure response dogs. Not all the service dogs that successfully make it through the training are good seizure assist dogs, so you are certainly lucky if you have found one. The animals trained at their facility go through a rigorous process that includes not only assistance tasks (such as retrieving dropped objects, opening and closing cabinets and doors, turning on and off light switches, etc.), but also behavioral training such as obedience and appropriate behavior around other animals (not just dogs and cats, but also horses, goats, etc.)
The breeds they use are generally retrievers and Labradors, but in the past have also used retriever/poodle/labrador mixes. They have a breeding program, so the puppies are usually selected for potential training before they are conceived.
I know there is a waiting list that is quite long for dogs that are trained at their facility. And I think that the dogs usually choose their humans, rather than the other way around. The training facility pays for the dog's healthcare for it's entire life, so the recipient doesn't have to worry about that expense. Training for the dog usually takes about a year and a half.
We have been to a variety of businesses (including many restaurants) with our kids when they have had a service dog with them. There has never been any issue at all with having the dog along. Of course, the dog always wears "the uniform", which is a service vest that clearly identifies the dog as a certified assistance animal.