I am to make my first wedding cake and they want one carrot cake layer, one funfetti layer and one coconut layer. The cake is to be a three tier square. Does anyone have any hints or suggestions on how to stack these? i.e. which on the bottom, is this too many types, is there a frosting that would go with all three?

i would do the carrot cake on bottom, it tends to be a moist (heavier) cake. Then coconut and funfetti on top. Of course most like cream cheese frosting with carrot but you could just use buttercream for it all. Good luck on your first wedding cake.

You'll need to find out how much they want of each flavor. Obviously whatever is on the top tier there will not be nearly as much as what is on the bottom tier. So i would do it based off of how many servings they want of each flavor.

Even though carrot is a heavier type cake it can bet the top layer. Cake doesn't support cake, your support structure does. You could put a heavy pound cake tier on top of an angel food tier.