There really is nothing wrong with mixing some wet food in with dry… I do and I really would not want to go through life just eating old dry food...;) .... the main thing is to be consistent in building good eating habits... same as with kids...
Yes, and a big benefit to adding some wet food to a their meal is that if you have a dog that does not drink enough or you are worried about dehydration this is a really good way to get them some fluids.
My dogs get dry food in the morning and wet mixed with dry in the evening. I usually add a little extra water in with wet in the evening just to make sure everyone is staying hydrated.
Urinary infections and crystals are far more likely if an animal isn't getting enough to drink so I think of the little bit of wet food as preventive medicine.