A 10X10 or 100 square foot barn seems a little small for how I perceive your plans unfolding. You will likely need something bigger to store hay or other feed in for your goats, chickens, and dog, besides providing more room for your flock, (Chickens won't forage much in fowl weather) they'll stand around in the barn waiting to get stepped on by a goat. Also if you want them to roost safely they will likely need a 8 foot roost so that requires a building with a 10 foot in the clear roof. This would also be a nice place for your great mastiff to sleep [f you can keep your goats out of the dog's house, sort of a dog house housed inside of a barn. Then your mentioned large livestock. They need a lot of room just to keep them from tearing the place apart when they fight. I would advise you to look at a 30X30 foot barn and build it high enough so that in the future you can add a lean to shed on each side to house equipment or other accouterments of the rural like style.
Regardless of your dog's jumping abilities I would think of a fence to keep your goats confined as the major expense. If your dog gets along with your fowl already, a high tinsel strength electrified fence may prove more practical to keep both K9s, and goats confined. As the humorous Mark Twain once observed, "A bill goat can get out of a 10 rail tall fence." I have seen a whole heard of full sized goats walk the narrow edge of a 2X4 (1 1/2 wide) fence brace and then jump on top of a 4 inch fence post one at a time before jumping to the ground outside of the pasture fence. Do you have any near neighbors who would object to a hen or two crossing the property line? By the way, goats binge on any grain based feed, even dog food.
Regardless of your dog's jumping abilities I would think of a fence to keep your goats confined as the major expense. If your dog gets along with your fowl already, a high tinsel strength electrified fence may prove more practical to keep both K9s, and goats confined. As the humorous Mark Twain once observed, "A bill goat can get out of a 10 rail tall fence." I have seen a whole heard of full sized goats walk the narrow edge of a 2X4 (1 1/2 wide) fence brace and then jump on top of a 4 inch fence post one at a time before jumping to the ground outside of the pasture fence. Do you have any near neighbors who would object to a hen or two crossing the property line? By the way, goats binge on any grain based feed, even dog food.