I don't think I've seen a recipe call for milk. I actually wonder how that would work out?I think I would feel better is there was less flour, maybe add some shredded carrots or something to that effect and lessen the amount of flour. But otherwise, I'm sure the dogs would go nuts for them.
I would substitute the flour for spelt flour. But if your dog has no issues with wheat, then it should be fine. I have used milk and cheese in my dog's treats before with no issues.