Rather than exporting as a TIFF format which limits white balance and other PP options, will exporting as DNG be the same as if I downloaded the files from the camera but with the latest adjustments saved?
Here's what I'd do (and do): get yourself a nice, big external FireWire drive. Put everything LR needs on that drive and nothing more. All images, the LR catalog and associated files and set the preferences for storing presets with catalog. Use DNG for all the raws. No sidecar files, DNG profiles embedded with instructions etc.
Now you have a drive you can clone quickly (after the first backup) that you can take with you back and forth. You can of course clone that to other drives as a back up. Use something that quickly clone's only new changes to the drive (on the Mac I use SuperDuper). Now you have a drive you can take anywhere that is always up to date. You can even run it on a different person's machine with a different OS and since everything is on the drive, you're fine. Just as long as the machine has a current copy of Lightroom. You end up with a good backup schema and you always have the latest data with you. The backup will not take that long (certainly not much longer than saving out DNG's to a thumb drive).