Very OOC for both of them. Your premise and set-up is okay, but you need to consider the fact that 1) Gaara is mostly asexual and not likely to initiate sexual contact, and 2) Sasuke is a powerful ninja who wouldn't just let Gaara rape him without fighting back.
And let's face it, would Sasuke ever admit to liking any sexual act? And would Gaara ever say something like "you're just too delicious" to anyone, let alone Sasuke?
If you want to write about Gaara and Sasuke together, that's fine. I've even done the occasional GaaSasu fic. Just keep in mind what the characters are actually like when you're doing it.
Not all yaoi is OOC, but the way you've portrayed this relationship is.