Oops, just realized I forgot to post what I did last night, things got a little busy last yesterday afternoon.
Anyway, here's what I did. Since I was seeing my mother last Sunday, but won't be seeing her this Sunday for Mother's Day since she'll be back in Florida, I figured that I need to deal with her present, the golf shirt, before I gave it to her.
What I did was I call up both stores last Sunday and asked to speak with the manager reguarding a billing issue. I explained what I had found when I looked at my receipt, and the scenario at the checkout of both stores. Both manager's told me that they appreciated my honesty and told me to keep the items free of charge, even though I offered to give them the SKU #'s of the socks and the shirt and my Mastercard #. Nice customer service move on there part IMHO, and since I'm already a member of each places basically frequent buyer program, I was going to be giving them more business in the future anyway.
I explained things to my 4 year old, who didn't quite grasp the entire concept, since when my Mother opened her gift, my daughter's words were "Nana, Daddy got you this shirt and didn't pay for it!"

Oh the things kid's say sometimes
