If you have an annual pass, you'll get the 10% discount too. Some of the hotels have penny press machines too. There's a web site that lists the locations if you're looking for a specific penny design. Guest services at City Hall MK is supposed to have a list too but I never asked for it.
You might want to wait before putting your pennies in the book if you want them grouped by category -- liked the characters together, movie characters etc. While you can move the pennies around, you can damage the plastic by having to pick the pennies out of the plastic.