I would suggest looking at various websites such as the following one:
You can see the current prices listed for what you have, which are around $25-$30.
I'd also suggest that the collection that you have is historically valuable for your family, and that you preserve them to hand down. You can get archival post card holder sleeves from www.universityproducts.com, for example and a binder so they can be handled and looked at without damage.
Please let me know if you have any other questions regarding antiques conservation/preservation.
Please rate my response, which was full and comprehensive, so I may be paid for my work.