That's sad for you, I know how attached to him you must be. If you're doing this for him, you're a wonderful person to put the pup first. This is a hurdle, at this age, while they're still young and foolish. This is probably the most challenging stage: after the landshark, and the older puppy - like when you got him.
My first GSD hated children too, and he was an adult when I adopted him. But I knew he didn't like them, and I kept them apart, and I didn't have kids anywhere near me IRL, so it was simple. You don't have it that easy. But before you find him a new home, please be more careful with him. Please don't leave him tied up outside where he can be a danger to himself, and to others. This is really serious, when he's nipping people (anyone can come up to him) or he's fighting dogs (same thing can happen). You need to be aware that with the DOLA, your pup can be seized and PTS if something happens, please don't leave him unattended any more.