There is a compilation serial number chart for prewar Schwinns that was posted here on the Cabe awhile back, and I just took it from there.
Large regular spaced digits in the same style as post war Schwinns,
1939 A00100-C10999
1940 C11000-E53499
1941 E53500-H99999
1942 I00100-I98189
As for keeping the bikes versus selling the bikes. It just depends on how much you love them. I'm sure that there are many people here that would like to have them if you should decide to let them go.