Can cupcakes still be fresh say after baking them Wednesday night and serving them Friday?

I find that cakes and cupcakes actually taste better with a little "sit time", if they're made from scratch. Just be certain to store them in an airtight container. I don't think refrigeration is at all necessary.

Also if you freeze them in an airtight container, you can pull them out a few hours ahead of time and frost when thawed. I've done this a couple of times.

Yes! Just keep them in an airtight container and don't frost them until Friday morning.