My vote---Hand quilt with a poly batt and outline about 1/4" from the seam with something pretty inside the square if you think it needs it. With that being dark, it may not show though. Maybe need an echo stitch if you think there is too much open area in the triangles. One of the advantages of hand quilting is that you can maneuver the fabric to take out the wobbles and puckers! Such a pretty quilt top that the quilting will only enhance. A treasured piece with two generations having made it!!