I think an appraisal tucked in with the quilt is a good idea. Even if they do have great sentimental value for the quilt (and you can't guarantee that) they might not understand the actual $ value of it.
I know people I give small quilts to are constantly telling me I should sell them, and then when I tell them I couldn't make enough money for it, they are shocked. Sometimes they'll even say something like "I mean, I'd pay $50 at least for this!" and I laugh and say materials alone cost $120, not to mention time, they just have no idea.
Knowing the cost of it might make the difference of being stored in acid free paper in a climate controlled closet, vs folded and put in a plastic bag in the attic if it ever does get put away.