As long as your dog is able to chew the dry dog food you certainly can mix wet can dog food with dry dog food.
Sometimes a dog will eat the dry dog food better when you mix in wet dog food along with the dry dog food.
But if the dog is a really picky eater then the dog might just eat the wet canned dog food and leave the dry dog food.
You can also add a bit of broth or water to some dry dog food to make it softer for the dog to chew and they'll usually eat it better that way.
I had a dog that I had to add some chicken broth to his dry dog food to get him to eat it and the chicken broth was healthy for him too.
I tried mixing some canned food with the dry dog food but he just pushed the dry dog food away from the canned dog food and ate only the canned dog food.
But once I added broth to the canned and dry dog food he ate both just fine.
But it's okay to mix the dry and canned wet dog food together if you want too and if the dog will eat it and the worse that will happen is the dog doesn't eat it or only eats the food it wants too.