You could also just have your Lightroom library on a portable harddrive along with the RAW files. When importing, choose "reference files in existing location." Then, direct your various versions of Lightroom on your laptop and desktop computers to find your Lightroom library on the portable harddrive. Whatever changes have been made are in the Library and accessible from any copy of Lightroom running on any computer.
Of course, this won't work when you've run out of space on your portable HD and need to delete files, because then the Library won't be able to reference those files anymore. So exporting as described above would work better in that circumstance.
Yes, this works too. It's even easier and better than exporting to DNG.