I have never had an American Bulldog myself but I've heard so many positive things about them. I follow an American Bulldog Rescue group on FB and I see many who are adopted into families with kids and toddlers. How did your son react to her? She sounds like a lovely bully and I'm sure she was just super excited to be around someone closer to her "level" (height-wise). You should ask a lot of questions to her current owner or foster as far as temperament and behavioral history which I'm sure you've already done. Sounds like a wonderful idea!