I am going to tackle my first fully fondant cake tomorrow and have a couple of questions. First- Should the buttercream layer underneath be thin or is it ok to put a nice thick layer on? Next- the party is Saturday evening, and I know I shouldn't refrigerate it- but will the fondant dry out while it sits for a couple of days? Or should I wait and do it Friday night???? All three of my kids have a birthday this week and I'm decorating 2- 2 tier cakes and some cuppies between now and then and want to ensure that they all turn out yummy as well as pretty. With all of the other cooking I have to do I'd like to knock this one out early in case I mess it up ! 
Any advice is welcome. Thanks!
Wow, you have a lot going on...I think that I get all my cakes baked and buttercream, fillings,even colored my fondant in advance, but as per decorating I think wait it out as long as you can before decorating.....I have leveled, filled and crumb coated the cake a day in advance and then the night before decorated it...it works out good. Good luck, your kids will love it......
The fondant cakes will keep fresh longer than the cupcakes, so make them first 
Two days in advance is fine for a fondant-covered cake. It's easier to cover a cake that has a thin layer of buttercream, because otherwise it wants to smoosh out when you smooth the fondant.
The outside of the fondant will dry out a bit but the buttercream will keep it soft enough to cut and to eat.
Hi and Welcome to CC, cindycraig. 
Decoding CC acronyms:
http://www.cakecentral.com/cake-decorating-ftopict-2926.html
Everything you need to know to make, decorate and assemble tiered/stacked/layer cakes:
http://www.cakecentral.com/cake-decorating-ftopict-605188.html
HTH
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