"But no matter it is to be put to charity quilting!" I am offering my opinion here. I would suggest not requireing that the fabric be designated for charity quilts. It puts undue pressure to be honest or dishonest with what was donated. reciently a local quilter with a massive stash passed away and one of her friends sorted through her stash and brought some lovely cuts to our guild meetings twice. Both time it came with the requirement that we could take the fabric but only if it was to be used for charity quilting. I and several others walked away from the table of fabric because although the intent is nice, we found it impossible to promise that the fabric would be used only for a charity quilt. Once a piece is in my stash it is there to use for any purpose, any quilt I am making. A small thing but perhaps an unneeded pressure. If you want to gift you stash to your current guild or your past guild, give it to them to use as they choose.
I was the happy recipient of my sister-in-laws stash when she passed away with ALS. She was a master quilter and did marvelous work. That was 20 years ago and I am still using her stash, her tools, her books and yes, I have made all of her grandchildren quilts from her stash. It has been a blessing and I continue to make quilts and give them away in her honor as my "missing mentor".
Yes, make plans for your stash. My plan is to keep diminishing the stash year by year and to then give my one quilting daughter a first go at what she may want and the rest to my guild.