Mean Male Cockatiel

I just got a Male Cockatiel from a lady who had gotten him because he had flown into her neighbor’s backyard. I had currently had 3 Cockatiel babies who are 3 & 4 months of age who had all been hand fed so they have known no harm. This little guy LeRoy looks like he is an older bird than them. He is friendly but it is on his terms. He will fly and land on your shoulder and be persistant on having his head scratched even turn his head from side to side. When you get him mad, however, he will reach out and peck the holey you know what out of you. I have noted already that he can sense the tone in your voice and responds by your reaction. If you are calm then I noticed that is when he will remain calm. I was just wondering if the more we work with him if this is something he could eventually grow out of and learn to trust us or is it something because he has already been loose out there could this be a bad habit that he’s picked up. I have 2 kids ages 3 1/2 and 5 and I’d hate to see him bite either one of them that’s why we only let them hold the babies who have been exposed to humans at a young age. Someone please help!!