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.)

Like the others have said, you are looking at using 2 mixes to get 2 inches in height out of your 9x13

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.)

I agree with Indydebi. I use Betty Crocker and 2 cake mixes. I used to only put 1 1/2 but, it didn't make my cake high enough. It tastes better now, before when I didn't have enough batter, the sides were hard.