If I bake and decorate cupcakes on Thursday will they still be fresh on Saturday? Or should I bake/decorate on Friday?
if you freeze it will be as fresh as you just baked the same day. not refrigerate though - freeze.
Cupcakes cool very quickly so I think you would be okay to bake and decorate all on the same day. Of couse, that depends on how many you have to make since too many may too overwhelming for one day.
As long as they're packed tightly together in a sealed container--like Tupperware--they should be fine. Your biggest problem would be that they would dry out. As long as you address that you should be fine.