I wouldn't let your dog near her or her babies at all right now. Stray cats are very protective. I took in a pregnant stray, finally got her used to me, and once she had the babies her personality changed for the first few weeks, she would turn on a dime if she thought you were going to touch them.
Once the kittens are old enough to walk around and she lets them go away from her, I would say you should be able to interact with them more.
If your dog is that fiesty with other animals, you can try getting thier scent on a blanket or something and then put the blanket with him. I have heard that if each animals scent gets on the other, they take to eachother better.
The kittens should have no problem getting used to him, they might be skiddish at first but they will get used to him.
It's cute when they first see a dog and over react, they stand on their little toes hissing with all their hair standing straight up.
