"Sleep tight, don't let the bedbugs bite!"

If you want to say it to little children you can say; nigh nighes now or bye byes now.

nighty-night (if I spelled it right)

Pleasant dreams, have a good night/sleep, sweet dreams. :)

?: ) :- ) "Don't let the bedbugs bite" is very funny. In the modern manner should sound like "Don't let the mob to call"