I regularly travel on the road, create "travel" catalogs and then combine them with my master catalog when I get home. The way to do this is to highlight all your images, select "Export as Catalog" making sure to check "export negative files" (i.e. the RAW files) and if you want to export the previews as well, check "include available previews." Then name your export and go to your master catalog and click "Import from Catalog"
Exporting as Catalog is crucial, as not all information is stored in the xmp files. Specifically, the following data is stored only in the catalog and not in xmp files: develop history (although the current settings are in xmp), collection information, virtual copies, stacks, and a few other things which are relatively specialized.
By exporting as a catalog and checking export negative files you will capture all the information about your images and also make sure that both original RAW files and the related xmp files are moved into the new catalog. Once you get into it, it's very easy, and saves moving files by hand and possibly missing something.
This is also why it is important to back up both your catalog and your images, whether you push data to xmp files or not.