I need to bake (3) 12'' cakes, 4'' high, can i bake (2) 12" cake pans at once in the over, 1 cake pan on the top rack and the other on the bottom rack?

I always have.

You may have to rotate them. Stagger them if you can to help with the circulation. And don't be surprised if one gets done before the other.

I have baked up to 4 cakes at once. Whatever fits is what I do. Just stagger and rotate them like peg818 said and check on them frequently. The baking time will be affected.

I did this two days ago. Just make sure you use a heating core or flower nail in the middle. I put one more to the right and the other one more to the left. They didn't overlap too much and both baked perfectly!