Several years ago, some foolish people put RAYON (an explosive) pjs on their kids with the predictable and horrible results. The outcome of this was laws requiring flame retardant (but unhealthy, IMHO) materials for kids. Yes, the laws need to be improved, but probably won't at this date. Yes, do make cuddly flannel backed quilts.
In case you have any doubt that rayon is explosive, try the experiment my father showed me. Put a scrap of rayon in the sink and add fire. My father, based on his scientific training felt rayon should be banned for all clothing, as a windblown spark from a passing smoker can turn your lovely blouse into a torch.