I'd be concerned about that too...and that the sugar would gum up. Then I thought
maybe you could cut them in advance, then do the sugar when you're ready to decorate but I think the surface would probably be less sticky. Hmm...I'm afraid this might be a "day of" project.
Hubby and I are having a 20 year anniversary party for 80+ this summer and although we are having it catered (it is at our home) I was going to do the entire dessert table. But 'day of' won't be possible for the most part (not to mention I'll have about 18 guests staying with us too - lol).
I'm going to do a test drive this weekend - making mini white cupcakes with a dot of raspberry jam in the middle.