I've found that the grandkids do not complain, in fact they have experienced the other side of the coin and rather appreciate having clean sheets. The way to get them to change their own beds without a fuss is to make it as easy as possible. Our oldest granddaughter has memory issues so I put the twin sheets on one shelf and the double sheets on another. I label the shelves as she can't remember what twin and double mean. If you think about it, double and twin both mean two so I get the confusion. By the word twin I put the number 1 beside it and double with 2. I could become frustrated and angry for yes, we have had most of the same sheets for years and they have not magically changed size but I suppose to a kid, the memory of what is what is not up there at the top of their importance list. I say, pick your battles. Life is hard enough as it is, especially for these sweet granddaughters of ours.
This is my linen, puzzles, and games, closet.Next step is to making it easier for everyone is to fold the flat sheet, fitted sheet, and pillow cases all in one bundle so the kids can just grab a set for a bed and go to work. Place the flat, fitted, and pillowcases separately and you might find the kids only use the bottom sheet and pillow cases or refuse to make the bed at all. If you don't have matching sets then at least form a set from the mismatch that you have and bundle together. Our oldest granddaughter has had some pretty heated arguments with her mom as she says it is easier to fight than to figure the sheet mess out. I get it and have done my sheets this way since our children were little. I have memory issues too as does my husband. I would have to say I do this in part because my linen closet stays neat and orderly because the bundle of sheets are thicker, the kids can handle them without disturbing the others. I do the towels in a way that minimizes the mess also.
Love at home begins with putting others first. It is not about what is more convenient for you but what makes things work more smoothly. If I keep a schedule going with things fairly predictable, and our belongings in order then I find that we go several days without a disagreement from the granddaughters. In this setting, surprises are most appreciated.