I have never done a wedding cake before and want to be prepared! It will be a 3 tier, probably heavy. It will be covered in fondant and have fondant swag trim/border at the bottom of each tier, so I assume I can't assemble there. What is the best way to handle this?

Yes, dowel each layer and be sure to put one long dowel down thru the center, sharpen the end with a pencil sharpener (cake dedicated) and tap/pound down thru all layers and into the base........Oh, and one other MAJORLY important step - be sure the cake is chilled well - I realize that may be difficult with the fondant, but if you use fillings that in any way loosen up when coming to room temp then you will end up with a disaster!! I speak from recent, murphy's law inspired, experience!! I have transported tiered cakes before and had one to do for last saturday. I stacked and doweled the bottom three tiers then put the longer dowel down thru the center, the top 2 tiers I had separately in boxes. Half way there I hear a noise.......sure enough the top 2 stacked tiers had fallen off and torn up the bottom layer ....Needless to say I had to rebuild the cake and it was only 3 tiers tall, with the other 2 in the back to be served only. I don't want to scare you but this definately put me off transporting anything over 2 tiers prestacked. The only thing I can think of is the cakes were not chilled enough (buttercream problems) and everything just went!! I have never had this problem before but it only takes one time to change your mind! A trial run is always a good idea for every part of your cake!

I am feeling VERY nervous about this! The drive is only 5 minutes from my house, but I don't want a cake disaster! I don't want to change the design of my cake, I'm kind of excited about it! AAHHH!

On a 5 min. drive, I might not be so nervous about the whole thing. The drive I had was 35 min. across town in warmer than average heat (mild for CA, but still warm) and the AC hadn't cooled the car enough. If you pre-cool your car, have your cake chilled (can be done with fondant) and well doweled you should actually be okay. Can you practice before the big day?? Even if you just do a cake with a straight mix and cover in Wilton fondant ... this could be the real test since regular box mix is not sturdy enough to hold up well under fondant. If you could try it this way and it makes it then you will probably not have much problem with the real thing!

Best of luck!!

I don't really have enough extra supplies to do a test run, the budget's kind of tight and I'm not getting paid for this, it's a favor - my mom's buying the supplies I need as they are her friends. I would gladly make extra out of my pocket if my pockets weren't empty this week - can't even get much for groceries (only temporary because of DH's job change).

I'll just have to decide if I feel like it will stand up to the drive! I was going to try the WASC recipe or the best white cake II recipe? Firm enough?

Don't worry! I've transported a 3 tier fondant cake, assembled, for much longer than a 5 minute drive, with no problems. Eg, the pink and white moth orchid cake in my pics was transported assembled, with dowels and a central dowel.
If you put some royal icing (firm peak) to stick the tiers together 12-24 hours before, you might be able to do without the central dowel if this will stuff up your design, as you are only taking it for a 5 minute drive; as royal icing dries like cement. Put it in a large box lined with non slip shelf liner, and put same liner under the box as well.

Renaejrk, the WASC recipe is a nice firm, dense cake. I use it all the time for carving and stacking. As I said, if possible to have the cake well chilled and with all the doweling it should be fine. As redred said, be sure to have some of the non slip shelf liner under your cake and the base won't move... you can find it at Dollar Tree (you'll only need one roll)...only a buck and consider this a must have!! It would be a shame if the cake would have made it except it slid against the side of the car!! You can reuse it so save it for future projects. Don't worry about not being able to do a test run just plan your project out ahead, bake your cake a couple days before and wrap it well in plastic wrap and put it in the fridge. This will actually help it to stay nice and moist and to firm up some, also seems to cut down on the crumbs. A tip on the dowels....you can find cheaper dowels than the pack of Wilton elsewhere in your craft store, near the rest of the regular dowels. Now they don't say food safe but they are hardwood also and that is the main reason people use Wilton (hardwoods don't splinter easily). If you want to sterilize the dowels to be sure they are food safe, then simply bake them in your oven at 350 for about 10 -15 minutes. If you have any other questions you can PM me or just post! Some wonderful CC member will help you out!