I am donating 10 sheet cakes for a benefit in a week or so. Nothing fancy. They will be baked and served in the disposable aluminum pans. Is there any way of baking these in advance?
Sure! Why not? If you are worried that the cake will get freezer burn, just cover with plastic wrap before you place the dome lid on top or instead of the dome lid.
So bake in the disposable pans they'll be served in? Once cooled do I just Saran wrap and freeze? How long to thaw? And do I frost then freeze?
So bake in the disposable pans they'll be served in?
Yes, that's how it's done (you said they'd be baked and served in the disposable aluminum pans). You might want to spray with Pam first.
Once cooled do I just Saran wrap and freeze?
Yes, if baking them in advance, just Saran wrap (or Press 'n Seal) the top surface or just use the lids if they aren't going to be frozen for very long.
How long to thaw?
It doesn't take long20-30 minutes for 1/4 sheets, or less than an hour for 1/2 sheets. You said you were baking sheet cakes... if you mean FULL sheet cakes, they'd probably thaw in less than an hour as well, but I don't think they make full sheet sized disposable pans.
And do I frost then freeze?
After they are iced, I don't see any reason to put them back into the freezerjust leave them out at room temperature until they are delivered or picked up.