I would also recommend The Fabric Shack in Waynesville, OH and my other favorite store is Miller's Dry Goods in Charm, OH in the heart of Ohio Amish Country (Holmes County.) There are a couple of other fabric stores in Berlin, just up the road from Miller's.
When you say you are going to PA Amish Country, do you mean Lancaster County? If so, be sure to go to The Quilt Shack, 3137 Old Philadelphia Pike in Bird-in-Hand, PA. The owners are so nice and the prices are great. Let us know what shops you actually get to visit. Have a great vacation!