So, I ask: have you ever trained your dog to come to the barn? Have you had success with it? What strategies have you used? What skills/training tools are important to have?
I know that barns are often free zones for dogs, and my barn is welcoming to dogs as long as they're well-behaved. I also know that Arya is only six months old and though sweet and smart, very puppy-ish. If she doesn't have the chops to be a good barn dog, so be it, but I think she could handle it beautifully.
I did bring Arya by briefly last week just for a taste of it. She loved sniffing around, she ate one or two manure balls, and she was mildly curious and very wary of the horses. She mostly liked the BM's dog (who is very large and solid and can be intimidating, plus has a loud pseudo-aggressive manner to new dogs). In all, I think it was a good success.
The barn manager's dog has a command that sends him to sleep on the bench in the ring while she's riding or working with horses. That would be ideal, I think. Hannah has provided some excellent suggestions for reading and training materials, especially in regards to the "place" command, which I think would adapt itself well to this.