Steph, it isn't that you can't machine quilt Minkee, you can, very easily, as long as you remember that it's slippery. I've made quite a few baby blankets with Minkee backing and they came out great. Pin the three layers closely and you'll be fine. Quilt either large motifs or straight lines or wavy grids, and it really enhances the puffyness of the quilt.
I like wavy grids, here's how I do it. Lay the pinned quilt on a table, Draw straight lines all over diagonally, in only one direction, I use a yardstick for this. Move the yardstick over 3 inches and draw another line, then another, etc. I use a chalk marker that just brushes off when through.
Start stitching on one of the middle lines, but gently go off the line to the right, then gently return to the line and veer off to the left, then back through the line and off to the right again, just about a 1/2" to 3/4" to each side of the drawn line, a very gentle wave, and don't bother trying to make the lines match each other, they look better random. After you get to the last line on the first half, go back to center and start over again to finish the second half.
Now you repeat drawing lines with the yardstick , but now on the other diagonal, to form your wavy grids and stitch as above. I've used this quick pattern often with Minkee and it really makes it puff up between grid lines. Just don't make the grid too small, 3" to 4" apart is good.
Use a walking foot if you have one, if not you'll be ok.
Secret to quilting Minkee is pin, pin, pin. and don't try doing intricate motifs, they won't show. My girlfriend once did very large freehand daisy like patterns on each of the front blocks, that looked good too, but she's an experienced free-motion quilter.
Denise