Dogs and babies

I have 2 dogs. Both are small, an American Eskimo and a besengi/chihuahua mix. I am expecting and starting to get worried about my mixed breed boy. He isn't great with other people's children. When my niece (2 years old) comes over, she tries to play with him and he growls at her and kind of lunges at her if she reaches for him. He will however let her feed him milkbones and then he runs away with it. But every time she starts running through the house playing he starts growling again and getting defensive.