Another thing you should add is more sexual scenes. Like for instance the family goes to the pool and they leave early because Alyssa somehow ruined the bottom part of her swimsuit( personally I would say she tore them down the center revealing her vagina and anus). On the way back you could say the car was packed and because of that Alyssa had to sit on Alex's lap. Make up something that would cause Alyssa to be forced to sit on something that would go deep up her anus or vagina. Alex could find this funny and start to take advantage by putting things beneath and their being oblivious would tell Alyssa to sit down of be punished.