What to do with the 'undies'?

For the last 11 years, clothing storage has been a huge frustration to me. I don't mean the 'hijack your life and push you toward the brink of suicide' type of frustration, but a complete annoyance, nonetheless. After Baby #1, I saved everything that wasn't Similac/poo poo stained, and stored it in a spare room (we had three spare rooms at the time...wow). Fortunately, it was easily reachable, since Baby #2 came 14 months later and was also a boy. They were both born in winter, many clothes were able to be used again. As Baby #2 outgrew, the clothes were placed back into the tubs.
Then we moved, and once again I had a great storage area...a huge walk-in attic (not the kind you have to bend in half to walk into) right off of our bedroom. It was perfect.
Baby #3 came along in the spring, and she preferred pink to blue and was completely pint-sized, so only a few of the unisex newborn items were used. Since this little gal was the first daughter and the first granddaughter on the maternal side, she was given a wardrobe fit for a princess. As she outgrew them, her clothes were also transferred to the attic.
And we moved. House #4 (if you count the apt in which we lived for the 1st 9 months of marriage) is equipped with an overhead attic that is very narrow, and a shed at the edge of the backyard. Closet space is abundant, but out-of-the-way storage is a little more limited.
As we began to contemplate whether or not we would add #4 to the family, I began to get pretty edgy about all the kid stuff that had accumulated, but didn't feel that I could let go until I knew for sure what the future would hold.
Baby #4 came through liking pink, as well, and that was my cue.  Let the purge begin! 
I decided to have a garage sale (my husband will cringe if he as much as reads those words!), and pulled out stacks and stacks of clothes.  After the huge effort to match, price, and execute the sale, I was pretty disappointed.  Over the next couple of years, we had garage sales a couple of places, and I would pull out the piles again and again, getting rid of a lot, but still having way too much left. 
I felt like I needed to get some money from the clothes (as opposed to dumping them at Goodwill) since I was constantly needing to update wardrobes with bigger sizes.  Any little $ would help, right?  But the hassle just wasn't worth the meager amount we would take in. 
So, I began passing everything off to other kids in the church who would be able to use them.  Bags and bags of nice clothes.  At one point I was starting to think that it might be overwhelming for the mom who was the biggest beneficiary so, knowing that she has a small house, I asked if she wanted more or if she was maxed.  She indicated the latter, so I was back to square one.  I didn't like the idea of consignment with the waiting for payment, etc.  I sold lots of little girls dresses on Craigslist, advertising them together in sizes.  That seemed to be easy enough, but still a little complicated with meeting people, etc. 
Finally, I decided to sell to Once Upon A Child.  I was pretty amazed.  I had purchased items there, but never sold to them.  It has taken me a bit to get the hang of it, but I seem to do better each time.  People are always interested in hearing about how to sell to them, and I will do a post on it later in the week.  It's not rocket science, but I have found a few tricks in being successful with this company.
My real question is, what is the best thing to do with good, used underwear?  There are close to 20 pair of boys size M sitting on my dryer...waiting for their fate.  I have almost pitched them, but every time I get close I think about kids who have nothing and it makes me feel terrible!  Does Goodwill sell used undies?  I'm quite sure OUAC does not accept them.  Is it gross?  Should I throw them away?  Is there another alternative?  I don't want to have nightmares about underclothed children because of a bad decision.  :-)