Bunkbeds are one issue. Quilts for family members is another. I'm coming to terms with my small-footprint son and family just don't need and probably don't really want many more quilts from me right now. I still get to keep stuff at grandma's house though!
So for actual bunk beds placed up against a wall, you need to go for a size that maybe isn't the nicest to wrap up in -- except they are great for slightly large couch cuddles! Keep the width narrow, like 60" or under and the length long so it can be tucked in firmly at the feet with the sides basically too short to tuck well. Whether that goes up to pillow line, or further, is up to you, but add about 12" for the tuck.
And then there is the possibility of the bunks being separated in which case you basically just want twin quilts. I didn't get the fabrics collected in time for my own son's bunkbeds but maybe for my grandson. Or maybe he can have one at his house and one at grandma's. Or maybe it will be clear it is time to go to someone else.
https://www.quiltingboard.com/member...14-621640.html