Thank you for the ideas! The ziploc box was a huge hit. After I put it in the cage, the two of them tried to move it down the ramp. It was really funny to watch. Silly piggies, the box won't fit - that didn't stop them from trying.
Also, I caught Cutie eating from the grid hayrack this morning. I hadn't refilled the ziploc box yet and she was growing impatient. So they can eat from it, they are just spoiled!!