Oooh thats nice! Your Grandson will be thrilled with it.
I have recently started free motion quilting, and got thread breakage too. Am no expert but I found that I just had to tweak the tension until it stopped happening. I guess all machines differ (?) but I have a Pfaff 1122, and have to have the tension on 4 or 5, whereas regular sewing I only have between 1 and 3. I also think it broke if I moved the quilt too fast too. Just my humble, inexperienced opinion!
It's going to be great no matter what you decide, but I'm thinking if you did a diagonal grid across it, so some of it would be in the ditch (ie on the sides of the red striped diamonds) and some of the stitching would cross the none-ditch areas on the blue and white pinwheels. It would tie in with the diagonal lines in the piecing very nicely I think? A blue and white varigated thread would show up nicely on the white. Then if you are feeling brave you could free motion stipple on the border.
Send it to me, I've got nothing to work on at the moment (cash flow/fabric flow problems!) I'll do it for you!!! :lol: :lol: :lol: