I need to make the following cake and I will need to purchase the square pans but don't know if I should get the 2" or 3" and if I double 3" is that too high. First I was set on 3" pans but now I'm leaning toward two 2" cake layers and just using thick board under each tier to add the height. or maybe even 2 3" just for bottom...with or without a board in center??? any thoughts and tips about this and square cakes is appreciated!!! 

and how many pounds of fondant? I'm going with a 6, 9, & 12. would 5lbs cover it??