I wasn't too sure if the fabrics would work together, but now it is done I think it is ok. I started with the yellow fabric - there is some blue and green in it which doesn't show in the photos. The bag went together rather well, though a bit bulky to fit under the sewing machine towards the end.
Yesterday I was looking through some magazines and came across a pattern for a shoe bag which I think would go well inside the sleepover bag. Just have to find which magazine that was. It would not be hard to make one, but this one was really nice. Think I will go hunting tonight to see if I can find it again.