B&N DRM is based on your name and CC# on your B&N account. It's tied to the file, not the device or any outside software like Adobe.
You can re-download all your B&N books via the Nook for PC app and transfer or copy them over to your son's Nook (new or newly activated under his name and account). Then open any just transferred e-book. The Nook will ask for the name and CC# on the account you bought the books in if it differs from the one your Nook is registered to. Enter that (no middle initial for your name) and the Nook will store the info for all the other books. This way you can share books between different accounts without removing DRM.
This a rather long and detailed step by step but it's a pretty simply process
http://bookclubs.barnesandnoble.com/...s/td-p/1126396