Welcome!
When your son has a chance to scan some images, please post them, so we can get a feeling for what you have.
There are a lot of resources for the "I just
inherited a collection" question, including threads here.
This is a link to an article that gives a nice overall summary of stamps and values for the newbie, and as a bonus, the author is a member here:
http://www.philatelictidbits.com/Good luck! Looking forward to a few scans.
Cjd