To be honest it's not that great of a thing that you're only interested in lucid dreaming for sex. Not because your interest is sex but because it's your only interest.

Dream characters don't always do what you want. Sometimes, even if you're looking for, say, Angelina Jolie, the dream character can be very unattractive, and other times not even interested in you. There'll come a point where you'll realize that there are so many better opportunities than just sex in lucid dreams (and, frankly, if you get to the point where you have a lucid dream every night you will arrive to this conclusion), but you'll probably have to have several LDs before you even get to the point where you can have sex without waking up.

Just for an example about dream characters: I once had a dream--not a lucid dream, but one where I had a great deal of control--that I had a magical book that I could use to control things around me. I was experimenting and thought to myself, "I want a new guy to come to school tomorrow." Well, a new guy did come to school tomorrow. He moved just across the road from me and so got on the same bus as I did. While we were all going to school I tried to tweak his appearance (without saying anything aloud), and he became sad. "Oh, come on, man. That's not me."

Basically, what I'm trying to say, is that you might not have that great of an experience with LDing if all you're trying to do is have a bunch of DCs to screw.