I started reading Rice’s series at 13, and wasn’t even slightly shocked. Her vampires don’t fuck. There are certainly sexual themes, but don’t mistake the vampire books with the ‘Beauty’ books.
Thirsty by M.T. Anderson might fit. It’s a YA book about a sixteen-year-old boy who becomes a reluctant vampire in a mundane high school setting (except for the vampires). It’s solidly in the young adult genre (instead of incest and demons, there’s high school awkwardness and parents to hide the vampirism from, rather than existential angst and oodles of undead sex) and recommended for 7th grade and up. It seems catered to an audience like your son, in fact.
I think Christopher Moore’s vampire books are great, but you might want to check them out first. They’re more comic than gory and upsetting, but (at least in You Suck, which I’ve read recently) there’s a lot of sex, drugs, and (non-horrific) violence. But if you’d let your son read Kurt Vonnegut I think Christopher Moore would be okay.
Yeah, lot of mature themes, but not extremely graphic. Would have been fine for me at 13, but then I was reading stuff like John Varley’s Titan at that age, so I may not be representative. I’d say check 'em out if only for the fact they’re decent fast reads :).
Since they’re on the radar these days because of the HBO series, I’ll also say that I’m NOT a fan of Charlaine Harris’ vampire books. But they’re probably more mature than you’re looking for anyway.
ETA: Oh and very much in the anarchic comedy style of Moore, this isn’t bad and has a vampire, if it isn’t exactly a vampire story per se. About as racy as Moore as well ( i.e. a bit, but not enormously graphic ).
Cassandra Clare has a couple of good YA books out - the first one is “City of Bones” and the second is “City of Ashes” (and there’s a third one either just out or to be released shortly). I read the first one and loved it; had trouble finding the second one until I found out I had to look in YA. The protagonist is a teenaged girl, but the characters and the story line are sufficiently well developed that I don’t think that it would a problem for a boy. Mature themes like life and death (and becoming undead), but no particular sexual shenanigans that I can remember.
A second for Vampire$. I don’t recall there being sex in it - in fact, it’s a plot point that vampires cannot have sex, and one is mocked by the protagonist for it at one point.
Another for Stephen King’s Salem’s Lot. Classic.
I’ll also add Poppy Z. Brite’s Lost Souls. Totally loaded with vampire drugs, sex, incest, but it’s a great novel and will resonate with a kid that age like almost nothing else.
Dracula really is pretty darn good, and readable, even after all these years. If he hasn’t read it yet, I recommend it.
I seem to recall a 16-year-old boy getting a blow job in the bath from an older man.
I was just coming in to suggest that one. It has quite a bit of language in it, but I don’t recall any particularly graphic sex or violence.
Has your son read Dracula? If not, he should give it a try!
You’re probably thinking of Whitley Streiber’s The Hunger. I’ve never read Vampire$ so maybe it has a similar scene too, but that’s definitely a scene in The Hunger. Sexual content aside, I wouldn’t recommend The Hunger because it just isn’t very good. The movie is somewhat better, but it deserves its R-rating.
This is just what I was going to recommend. I think Thirsty was out of print for a while, but I recently saw it in the bookstore with a new cover. I remember it very well from reading it when it was a new book. It’s an interesting take on the vampire story and is much darker than most contemporary vampire fiction – it actually deals with the horror of becoming a vampire.
*Again just what I was going to say…seriously, are you me? 
I read You Suck about a year ago, but I remember that the protagonist and his girlfriend were having acrobatic vampire sex all the time. This wasn’t graphically described and was played for humor, but if the OP is concerned about content then I’d also suggest reading the book first.
I was about 13 or 14 as well, and I didn’t find them too adult. (There was plenty enough sex in the Stephen King books I was reading!) Then they started getting a little too emo for me and I stopped.
Yikes. Guess I either missed or ignored that scene.
Vampires edited by Jane Yolen and Martin H. Greenberg. I’m especially fond of “Curse of the Undead.” 
Also, it looks like there’s a “Vampire” entry in the “100 Little <genre>” series. These collections are usually pretty good.
There’s only one scene that’s iffy:
Sunshine teleports naked over to Con’s place and right when they’re getting hot & heavy, he pushes her away and runs out to put some clothes on.
I think that’s in The Vampire Armand, and I think he (and the entire “stable” of kids the older man in question had around) was considerably younger than 16.
I didn’t even know that book existed. I read Interview, Lestat, Queen of the Damned, and maybe one more that was mostly about Lestat feeling sorry for himself.
At this point, there are 10 books in The Vampire Chronicles. I have not read anything beyond The Vampire Armand myself.
That is a wise decision, says the person who read all of them. Actually, the best decision would be to stop with Queen of the Damned because Lestat suddenly gets a bad case of Catholic Guilt in Memnoch the Devil and mopes around the rest of the series.
Oh, I know. QotD was wonderful. Tale of the Body Thief was good, but I could see the thread holding up my opinion of her work starting to fray. Memnoch the Devil saw some of the plies in that thread snapping, and The Vampire Armand finally completely broke it. I haven’t gone back to the well since…the water’s all brackish and oily now…
The Last Vampire series by Christopher Pike seemed good (I only read the first two books in the series). It was published as six individual volumes (The Last Vampire, Black Blood, Red Dice, Phantom, Evil Thirst, and Creatures of Forever) or two omnibus collections. They were marketed as a Young Adult series so there’s some mild mentions of sex and violence but nothing extreme.