For prep, iron the top (and you can spray starch the top as you go, if you are good with spray starch), heavily starch the backing fabric, and I recommend spray basting with 505. Both the starching and the spray basting help to prevent unwanted puckers, especially on the back.
For the quilting design, if you have never done machine quilting before, the easiest way to do it is making gently wavy lines with a walking foot. Diagonal crosshatching could be nice. Basically you would start at one corner and sew a gently wavy line to the other corner. Then start at a different corner and go the other way. Work out from the middle.
All-over free motion quilting would look nice too, but free motion quilting takes quite a bit of practice to master.
Stitch-in-the-ditch makes me very anxious, so I don't do it anymore. It requires paying constant close attention to exactly where you are in relation to the seamline. If you are a perfectionist, it can drive you crazy because it is almost impossible to stay extremely accurate.
Stitching straight lines (with a walking foot) 1/4-inch inside the seamlines can be very nice *if* you can quilt straight lines from one end of the quilt to another. If you try to do it in a similar way to hand quilting, which sews a line inside each piece, you will have a lot of machine stops & starts which can be difficult to hide.