Can't help you at all with the pattern itself but I encourage you to go for it. I'm of the belief that you should do projects that you WANT to do regardless of difficulty. You will tend to stick with it through the difficult stages if it's something that you really WANT to do.
AND you get the benefit of establishing the type of relationship that you want with your sister. What could be better?
Plenty of help here on the board for those spots you might get stuck. Go for it!