flannel makes such wonderful cozy soft quilts- it would be a shame to not make your grand-baby's quilt oh so wonderful-
you can use a center layer of a single sided white flannel instead of batting- which makes it still soft and durable- but flat--easier to hand quilt=
you could get a high loft fluffy batt- and tie it
you could pick up a hobbs heirloom low=loft cotton batt- which is only 1/8" thick- also very nice to stitch through- and (thin)
you could make the top flannel- the backing oh so soft minkie--and no batting..
lots of options--
congradulations on the upcoming grand-baby to enjoy!