usually it's a lot more of a concern for the 2 legged types and what holes we cant see under a little bit of water; have had buddies walk through what they thought was ankle deep, only to go in over their waders - that ends the hunt pretty quick.
For the pups, two things I've observed to keep in mind:
Just like us, when they get older the joints aren't what they used to be; I've seen an overzealous retriever or two hit the mud hard and stop suddenly with a good yelp - the sticky stuff can wreak havoc on ankles, knees, shoulders, and hips.
Tidal flats collect garbage of all sorts; there's no telling what kinda sharp prickly stuff might be right under the surface.
Keep the dogs at a controllable pace and keep your first aid kit on hand, you'll be fine. (oh and maybe some extra freshwater too, if you don't carry already)