First of all, are you planning 5" tiers? When I bake wedding cakes I usually bake in 2" or 3" deep pans. Remember that you are going to be torting (slicing horizontally) into usually 1" layers within the tier. Then you will be adding filling between each and frosting as well as maybe fondant on the top. This will elevate a 2 inch cake to almost 3" and a 3" to at least 4". You will have to probably even the domed tops (which become the bottom).
Baking a 5" cake will be next to impossible and you will end up with an uncooked center and hard crusty edges. You can use the pans, just don't fill them.
What I do when I am baking large/thick cakes is to drop the temperature to 325 and bake longer. For cakes 12" and larger you can/should get a heater core
. You set this in the center of the cake and fill it with batter (to the same level as the cake). The metal from the core heats up and helps to bake the batter around it. You just remove the core and stick the cake from it in the hole.
Another help to make cakes bake more evenly and not "puff up" is to use baking strips
. This link shows you various ones, though I don't think it would do much for a 5" depth.
I hope this helps. If you have any more questions, don't hesitate to ask. I have been doing wedding cakes for several years now and have the experience of many successes and failures behind me!