Both of them?

He heard a soft giggle and pulled open the shower door, to see both Holly and Kristin standing there, naked. Kristin smiled and turned her face to her friend, kissing her cheek and purring just loud enough for Peter to hear her. "See, Holly? I knew he'd be nice and hard... Probably jerking off, thinking of our hot little teenage bodies. I wonder if he imagined all three of us together, one of us with him, or you and me together?"

Holly giggled again and stroked Kristin's bare ass. "Why don't we ask him, since his cock is all nice and hard." She purred back and stared hard at Peter. "Well? Did you want to fuck one of us, both of us, or watch Kristin eat my horny little cunt?"