OMG that is BEAUTIFUL! You'll post pictures as you make it, won't you? Please??
To me, a shawl can't really be too big - you just wrap it around yourself all the more securely. So if it fits your mother, it should do for your 5'4" minister (btw, that's how tall I am). I like to take the ends of a triangle shawl and tie them then toss the ends over my shoulders - or maybe use a pin to keep it from coming open.
But a shawl that is too small? Nope, can't do a thing with it. No good, so give it to a kid.
That is sooo drop-dead gorgeous! You have really good taste. Not to mention knitting skills!