What do you consider the qualities in Atticus that makes him such a good father to Jem and Scout?

There are two other qualities that make him not only a "good father" but a great father.  He is honest with his kids.  He never sugar-coats anything to them.  When Scout asks what "rape" was, rather than getting flustered like Uncle Jack did, he gave her the clinical definition of it.  He told Jack that when a child asks you a question, you answer it.  It's that simple.  He treated them with respect by being completely honest.  He told them what they needed to know, and didn't make a "production" of it.

The second and perhaps the more important of the two qualities was teaching them courage.  He didn't want the children to think that "a man with a gun in his hand" was courage.  He was referring to when he had to shoot the dog.  That wasn't necessarily courage.  He told them that true courage was

"when you know you're licked before you begin but you begin anyway and you see it through no matter what.  You rarely win, but sometimes you do. Mrs. Dubose won, all 98 pounds of her."

Both of those qualities make Atticus a wonderful father and a teacher at the same time.