looks like Prunus virginiana, chokecherry. IF that is what it is, i wouldn't think it toxic, my mom made jelly from them as a kid, though off the plant the fruit is pretty bitter...
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I think so too. I've made jelly from the cherries and people make wine. The jelly was OK but not really worth the trouble. One thing with your dogs though- if a branch is broken from the tree and the leaves wilt, they produce cyanide. The dogs aren't likely to eat them, but cattle and horses are often killed. Also, at least here in Kentucky, they attract tent catterpillars like a magnet. Still, they are a native tree and valuable as food for birds.

Thought it was chokecherry, but am glad for the more expert id above. I discovered by accident that the fruit sweetens up considerably when it dries, and becomes quite tasty, if chewy.

one other thought re: your dogs. the inside kernal in pits of cherries also contain a small amount of cyanide. I would imagine that the dogs would pass the stones whote, but I might try to control the amount they have access to if they are really gorging