Hi Moose, I have had "professional gardeners" !! who have done things like that. Dogwoods should be pruned down to about 6inches in March time. I am sure that as yours are well established, they will be alright. Perhaps you could say sorry to them and point out that it wasn't you
and just protect them with a shallow amount of fine chip bark or similar. Don't feed them and then with care, when the frosts have finished.
In the meanwhile, keep everything crossed, there is not a lot else you can do. Good luck, Mrs Bouquet