I'm pretty sure double jeopardy only applies to these particular charges. If he were to molest the same boy again (however unlikely that may be), he could be charged and tried again for that crime, just not for the previous charges.
Double jeopardy only applies to charges already tried.
It isn't the double jeopardy that will get in the way of another trial--it's just that after this one, I doubt most prosecutors will want to dive into another pointless circus like this one.