Wish I knew how to impress son and DIL with time, work, value and love that goes into making a special quilt for them. My own design, sampler style, photos, personalized embroidery, etc. and DIL still has it in the quilt storage bag given to them with the queen-sized quilt 7 years ago, even bought a quilt rack! So please find a way to save you much "distress" and let them know the "total value", made with "priceless" love.
I started a thread yesterday asking if a person got their feelings hurt when a quilt wasn't shown at all or wasn't used as intended. Most of the answers were along the gist of "You can't make a person like a quilt no matter how much you liked it while you made it. Some will never use it - some won't even keep it. When you give it away, forget it."
But I'm sorry your DIL and son won't use your quilt or display it on a quilt rack - at least when you come to visit if at no other time.