@Tom > You can just move the files from one folder to another on your harddrive without any problems.
Where the problem does occur is that rekordbox then looks for that file in the original folder. You can choose to relocate the track i.e. to the new folder you put it in. Rekordbox will then ask you if you wish to search the rest of this folder for the other missing tracks. Choose yes.
Thats it, once you have them relocated there is no need to re-scan.