That's a great idea. Better to start it, as you did, before the kids get too old. Our youngest son did that for us about 10 years ago (when he was 30). In addition to a box for himself and each of his brothers, he had boxes for us, my family, Con's family, houses, cars, and group pictures that could go into more than one box. It took him a long time. He also had a stack of pictures of people he couldn't identify - some of which we couldn't either!
Judy, I'll bet you could track down more of your father's family. Start with him, the aunt and G'ma and look in census data for the 30's. If you have any idea where they might have lived, you can narrow down the search to those states. I think it's doable.
Muriel