P.J., I can't help with your question but I'll bet some of the members who have already made the ornaments can help. Here's a link to a thread in Pictures in which Twisted Stitcher (I think) posted pics of the ornaments she made. A few other members posted comments in the same thread that they've made them or are making them. I suggest you send private messages to those members and ask them how much fabric they would suggest for the smaller balls in case they don't see your post. You probably know this, but just in case...to PM just click on their names, then click on the place that says "Send a private message to this member" or something like that.
http://www.quiltingboard.com/t-31032-1.htm
I love those ornaments and hope to make some, too.