IF you really have to quilt them, PLEASE do it in a more traditional way and don't McTavish them to death...doubt the fabric will hold up too much manipulation as it is. But to honor their age, use something plain on the back and keep the quilting traditional/heirloom quality.
Of course you do realize they might not quilt easily...so don't be upset by puckers, pulls, waving edges, etc..
I wish you luck. Do keep us posted when they are done!