Well, this isn't an issue I have had to deal with yet; it is something my gf and I have discussed in that 'what-if' kind of way; I have daughters by a previous marriage, and although they live with their mum, it might not always be that way.
Personally, if a kid is of age (say 16+), then I think it is by far the best thing if they can do what they are going to do somewhere nice. If they've reached that point, then if they can't do it somewhere nice, they will follow generations of teenagers and do it where they can.
That is my pragmatic, intellectual side speaking.
Emotionally speaking, if, in three tears time, my daughter was living with me and had a boyfriend she wanted to stay over... well, she'd be 14 and I think that's too young. I hope I'd be able to make her see it would be best to wait. I hope I would avoid chasing her boyfriend (or girlfriend) down the road with a baseball bat.
If I couldn't get her to wait, well... I'd rather she be honest and use her bed even if I disagreed, than be dishonest to please me or get off the hook, and I'd make it clear that was my opinion.
As regards your situation... well, I'd just say "Look, I'd far rather you be honest with me than spin a tall story to pull the wool over my eyes so you can do what you want. Your honesty is far more important to me than you blindly obeying everything I say, or trying to make me think you blindly obey what I say." It does sound a little unlikely, but truth hides in the stranngest places, so don't make assumptions! And realise that you're probably dealing with the stable door, rather than the horse. And, given the assumption it's gonna happen anyway, decide if you can overcome whatever discomfort you have over the issue in order to keep the relationship with your som as open and honest as possible.
I like your cheetah, by-the-way...