I am making a 12" x 2" round double layer cake for 30 people for this Saturday Oct 25th. I make my cakes from scratch and the recipe I use is for a standard 9" double. Can someone help me adapt this 9 " recipe for the 12" x 2" round double layer cake? Many thanks!

The Wilton chart has 9 inch round holding 5 1/2 cups while the 12 inch holds 7 1/2 cups.  So roughly  1 1/2 times your regular recipe. 

I think that leaves the 12 inch cake a little shallow.  I would go ahead and make double to make sure you can fill the pans appropriately.  If you have a little left over for cupcakes, fine.

AMany thanks!