Option 2 (Use XMP)
Your second option (not to merge) is to use XMP sidecars to bring your location shoot’s info into your master catalog. This option is a bit easier than the merging one and can be very effective for the task at hand, but it does have its limitations. The benefit of using the XMP option is that you don’t have to be nearly as careful about library folder positioning, naming or any of that. Just follow these step
1) Make sure your laptop is set up with a copy of Lightroom and plenty of hard-drive space for the number of photos you think you might shoot on location. Alternately, plan to take a portable, external hard drive for your photos.
2) While shooting on location, copy your photos to your laptop (or external hard drive) and arrange them into folders named with when, who, what and where in the folder name, or whatever folder naming scheme you use in your master library back home.
3) Create a temporary Lightroom catalog on the desktop of your laptop, or just use the default one in your pictures folder, and import your daily shoots as you have time. When planning to use XMP, you can add keywords, your copyright or other metadata, star ratings or color labels in the Library. You also can make any color correction or other adjustments you wish in the Develop module. There are just one or two limitations when using XMP that I’ll outline below.
4) At the end of each edit session, or at the end of the entire location shoot, write your accumulated catalog settings out to XMP sidecar files. This is easily done by going to the Library grid mode, choosing Edit > Select All, and then choosing Metadata > Save metadata to files. This will write the XMP sidecar files in your shoot folders, right next to each source RAW file. (If you’re shooting JPEG or DNG files, or if you convert your photos to DNG on import, the “Save metadata to files” command won’t write sidecar files, but will instead write the metadata directly into each file. This workflow will have exactly the same outcome as working with RAW files plus sidecar files.)
5) When you return home, copy your shoot folders from your laptop directly into your Master Library folder. (At this point, the Lightroom location catalog on your laptop is redundant. You never need to copy it to your home machine or archive it if you don’t want to. I recommend keeping it at least until you complete Step 6, but at some point you’ll possibly want to delete it.)
6) Launch Lightroom on your home machine, open your master catalog, and import the new shoot folders. During import, Lightroom will see the XMP sidecar files (or, the XMP metadata it’s written into JPEG or DNG files) and will duplicate all that metadata, develop settings, etc., into your master catalog.
You’re done! You’ve successfully integrated your entire location shoot into your master Lightroom catalog.