Were the children fond of Atticus? How do we know?

Yes, their relationship is close. Scout is very close with Atticus and Jem. Scout's relationship with Atticus is gentle and respectful. Her relationship with Jem changes as the book progresses but they are still very close. Calpurnia is a mother-figure to Scout. Jem loves and respects his father. He constantly tries to live up to Atticus's expectations.