I've already baked my giant cupcake. I am planning to use the candy melts in the bottom of the silicone mold to get a shell for the bottom of the cupcake.

I'll be away on vacation all of next week, so I'm wondering if I can put the completely decorated giant cupcake (including the shell bottom) in the freezer? The order (along with 50 cupcakes) is due the day after I return.

Has anyone done this?

I wouldn't trust it... I would think it would crack upon thawing.  I had one crack just leaving it in the fridge too long (overnight), it cracked almost as soon as I took it out of the cold.  I used Merckins chips & paramount crystals.

Your candy shell will be fine left out.  Just cover it to keep dust off and put it somewhere that it won't get hot.  DO NOT put it anywhere that it will be in direct sunlight.

I recommend doing as jgifford has advised.  I do NOT think putting the fully decorated cupcake in the freezer is a good idea since the candy shell may develop condensation, "bloom" (whitish patches on the candy shell), or crack as mentioned above.

Candy melts are best kept at room temperature in a covered (doesn't have to be airtight) container.

 Thank you for your advice!