I am making a 9x13x2 cake for my son's first birthday on Sat.
This is a new pan and I was wondering if this pan would need more than one cake mix?
Also how much icing would I need?
Newbie here!!
One cake mix should be plenty...I use about 5 cups of buttercream for a quarter sheet cake 
I use Pillsbury mixes and I have to use 2 for mine. If you are using a box mix, they do not all measure out the same. Here is a link to help you.
http://www.wilton.com/cakes/making-cakes/baking-wedding-cake-2-inch-pans.cfm
a 9x13 uses 7 cups of batter to get 2" of height
http://www.wilton.com/cakes/making-cakes/baking-wedding-cake-2-inch-pans.cfm
Depending on what brand or flavor of cake mix you use you'll need about 1-1/2 boxes up to 2 boxes. Different brands and falvors within thos brands make anywhere from 3-5 cups of batter (unless you're adding more ingredients to it as an extender then it'll make more cups.)
I use Duncan Hines cake mixes! I like a nice high sheet cake (2 in.), so definitelly use 2 boxes. Any left over, make a few cupcakes! Oh, and let me tell you I find the DH butter yellow cake mixes to taste wonderful, and are very moist. Just be very careful not to over bake.
As "just a mom" who is going to leave the cake in the pan and slap some icing on it, one cake mix will work.
As a caker, who is going to flip the cake out and who wants a nice tall even cake, and who is going to actually decorate it, I'd use 1.5 cake mixes. (I use Betty Crocker. Yes, the brand of mix will make a difference.)
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