Even when all are 18+ you never get too old for a sleepover.
Imagine laying on your back, blindfolded and with your arms tied to the bedposts. Your girlfriend is holding your head in her hands, massaging it while she is frenching you fiercely. You know her kiss and smell. At the same time two other girls are playing with your tits, kissing, caressing,squeezing,twisting, even lightly biting them. This triggers your orgasm, the first ever without any stimulation of your pussy.
You relax for a moment, thinking that it is over. Then, a fourth girl starts licking between your legs, slowly fucking you with one, then two fingers. She is soooo good at it, avoiding your clit in the beginning, and keeping you on the brink forever. Finally, she takes you over the top. You scream your orgasm into your girlfriend's mouth, while being taken from peak to peak, until your body gives up.
They hold and hug you while the last spasms leave your body and you still sob a little, not because you are sad, but because you are overwhelmed.
I can highly recommend it.