I would pin baste and then do the machine stitch-in-the-ditch quilting. Since you have 6" blocks, this quilting should stabilize the quilt enough that you can remove the pins before moving on to the hand quilting.

I am in the home stretch of piecing a signature quilt top for my church's centennial in November. It will be a fairly large piece, 92 x 98 inches. It has over 100 6-inch blocks, set with 2 inch sashing, and a center logo for the church. I am going to use Quilter's Dream mid-weight cotton batting. My quilting plan is to do machine ditch quilting along the sashing, then hand quilt the logo and a few details in each block. (The quilt will be in a frame for the hand quilting stage.) My dilemma is how to baste the quilt. Pin basting is good for machine quilting, not so much for hand quilting. Hand basting threads are hard to remove if you machine quilt over them. I'd appreciate advice from anyone who has mixed the quilting techniques.