I ended up using the walking foot and doing straight-line quilting in the sashing and border and then used a zigzag stitch to stitch over the seams between the t-shirt pieces. (I was afraid the seams would get all bunched up when it was washed.)
I used a grey batik for the back instead of the planned flannel. Made the quilting easier.
Emma and Smudge are breaking it in -
(she doesn't know it's done yet... I put it over her while she was sleeping!)