As a quilters, our "joy" has to be the construction of the quilt: the selection of fabrics, design, cutting, sewing. It has to be fun for you. Giving the quilt and the recipient's reaction is secondary. No one, except one who has made a quilt, can ever understand the sweat, tears and time that goes into a project of this magnitude.
Don't try to second guess your inlaws reaction. Finish it and give it to them and go on to the next project. For what its' worth, I think you were very thoughtful to make them a quilt and wish they would have responded appropriately.