Hmmm. I think the notion of “tummy time and heirloom piece” are a bit at odds.
In my experience, floor quilts are washed a lot and can experience a fair amount of pulling and rubbing against an applique.
They also need a thicker batt for all those times a head or chin slams downward.
Better, if you want a floor quilt, to use a different applique, turn the raw edges under, and stitch it down very close to the edge. A baby will love fingering the edge of the shape and trying to pull it up.
With my last one, I even took a matching polyester thread and sewed between the topstitching and the edge. It’s been washed a zillion times and still looks good, albeit a bit lighter.
hugs,
charlotte