As a retired nurse, I know u mean well , but freq the nursing homes are not able to use " ties" on lapquilts. It can actually be a hazard. The state can see it as using a resraint ( and restraining a persona against their will, even if for their own safety) is illegal.
I make alot of w/c quilts, ( for Veterans) I try to back mine with fleece or flannel. They tend to stay in place fairly well.
Nursing Homes staff are pretty adept at " tucking" it around the person.