make applescript close keynote after presentation is over
If you run this to kick off the keynote then it will quit Keynote as soon ( well within 5 seconds ) as you stop presenting (esc). If you want it to quit after you sit on the final slide for a preset amount of time then just say so.

tell application "Keynote"
    if not playing then
        start
        repeat while playing
            delay 5
        end repeat
    end if
    quit
end tell