Is it necessary to use stacked construction for 2, 12" x 2" heart shaped cakes?

Usually, dowels and boards are used when your cake will be 4" high and will have another stacked on top. Since it sounds like you are using 2 2" layers, you will be fine with no dowels and boards between the layers. 

2, 2' tall layers stacked is the normal size of a tier.  You only need to use "stacked construction" between tiers.

Unless as Dayti points out, you have a tier that is taller than 4" then you may need some internal supports.

Oh, Yay! Thanks so much....as you can tell I'm a "newbie"