there's no reason you can't use prairie points for a wall hanging. whether or not they flop forward will depend on a number of factors:
how floppy is the fabric in the first place? if it's pretty floppy, innerfacing will help keep it stiff.
how big are the p-points in relation to the body of the quilt? if they'll poke out more than 1.5", i'd suggest making them large enough to fix with a 1/2" seam instead of the standard 1/4". make sure you topstitch both in or near the ditch, then again at least 1/4" from the edge.