If I was in this situation I make a difference between thinking.... "gosh this boy is beautiful and I'd like to sex with him" and maybe even fantasising what I'd like to do with him... and thinking... "how can I get this kid alone and get into his pants?"... or "I wonder if he'd be willing to sex with me?"

The first kind of thoughts are simple acknowledgement of his attractiveness to me and my enjoyment of that. This, in my opinion, is not lust.
The second kind of thoughts, in my opinion, reflect intent and ARE what I see as lust.

So if I were in this situation... I'd pray like this:
"gosh Dad, this boy in front of me is so beautiful! He's so sexy too! I mean... just look at how delicious he is! Thanks for making such a spectacular looking person!!! Please help me to honour You and Him in my interactions with him. In Jesus name. Amen."

Blessings
Cat.