The Finder’s ‘duplicate’ command (which is used to copy files) takes any number of source files to be duplicated. so you can just:
tell application "Finder"
duplicate (every file of folder "Path:to:source") to folder "path:to:dest:" with replacing
end tell
You can get even more creative using ‘whose’ clauses, but the point is that with the Finder’s ‘duplicate to ’ command can be any reference to any number of items on disk whether that’s one file or thousands.