Both of the stamps were "work horses" and printed by the millions.
There is a very very slim chance the 1908 Ben Franklin could be one of the rare varieties. It is part of a complicated series of stamps called Washington-Franklins which you can investigate here.http://stampsmarter.com/features/SQ...rank_ID.html
But your great grandfather-in-law didn't collect the stamps so much as he did collect the postcards
With postcards, we have a stamp, a postmark, and some type of message, either a picture, and or a written message or both.
Far more likely to be more value in the cards than the stamps.