I would ask this as a comment but I don't have enough reputation (yet) so I'm starting with my comment/question, then will give an answer.
Are your photos in RAW or jpeg or other format?
If your photos are in RAW, (the use case I'm most familiar with), LR has the option to store the develop information in sidecar .xmp files. See this tutorial:
After saving the metadata (LR edit changes) to .xmp move the RAW files to a different folder, and import them again into a new catalog with the new date metadata (stored in the RAW file and edited with exiftool). Then after the photos are in LR with the correct date, move the .xmp files into the same folder, and then update the files with the "new" metadata. This should bring back all your LR edits while retaining the changed date.
Test it first!
Make 2 new folders. Copy a few RAW files to one folder, and copy their companion .xmp files to the other folder. Make a new catalog, import the RAW files and make sure the date is now correct. Move the .xmp files into the folder with the RAW and then tell LR to update the metadata and see if it works. If it does, you can delete these copies (you made copies, right?) and catalog, and do it all again with all the files.
I'm assuming you have many other photos in LR but for this process I'd make a new catalog just for these photos, and make sure everything is as you want it, then "import from catalog" to bring them into your main catalog.