DS LOVED the sibling class at the hospital, and if the sibling class at the birth center weren't at an inconvenient time he would be going to that as well.
At the hospital they took them on a tour of the ward, showed them all the different parts of the room. Then took them down to the education center to watch a sibling video, that talked about hand washing and how to act around the new baby and things to do with the baby. They practiced holding a stuffed animal like a baby. Then she took them to wash their hands, they painted a onesie. He had a blast. Totally worth the money of taking them, though that class was free, it is like 15-20 at the birthing center.
You could check the other hospitals in the area maybe? They didn't seem to mind that I wasn't giving birth there.