I want to offer a fully-decorated cake for a silent auction at a holiday fund-raiser in early December. I'm wondering if I could put an info card on the cake saying that it can be frozen if they want to use it a week or two later? I've never tried freezing a cake covered in fondant with gumpaste decorations. Will it work? If so, how should it be done? Any advice appreciated!

I wouldn't suggest freezing it!! You will get a ton of condensation when it thaws and even if it makes it through all of that you'll most likely get huge air pockets between the fondant and the cake because of the cold air trying to escape as it thaws and I know for a fact that the gumpaste will absolutely disintegrate from being frozen!!1
i would suggest making a smaller cake than you had planned and include with the cake a voucher that will allow them to have a bigger replica of that cake made for Christmas if they choose! Kinda like a two for one deal. Or you could have them auction the cake and then auction a coupon for that same cake at a date of their choosing! So if there are people that want it now they can have it and if there are people that think "hey I'd love to have that in 3 weeks closer to Christmas ", then they can have that as well. Buttercream covered cakes do however freeze beautifully!

You're a doll -- thanks! Exactly what I wanted to know. You know, if I did the whole thing on a cake dummy, maybe I could save the gumpaste decorations and use them on the real thing at the buyer's chosen date....

Be sure to put a clause in that coupon to prevent very last minute request and times you might not be available.
Like: 'must have 48 hrs notice' OR not available on (certain dates); this coupon expires (date).

Good advice, thanks!!