I have a dear friend who has the Bernina Quilt Frame, machine and Quilt Motion. It takes a while to get used to it, but she loves it and the quilting she does is magnificent! I looked into it (I have the Bernina Quilt Frame and use my little 440QE on it) but I'm not ready to spend that much money yet.
For those of you who don't know about Quilt Motion - it is sold for other machines under different names - is is control board that goes on your carriage under your machine. There is also a control that fastens to your quilt frame handle and you must use a computer to run it all. You select the design, designate the size of your block and it quilts it for you.
Good luck to you and your SIL. Can't wait to see the beautiful work you will be producing with your new set up!