Make them compete

Jim grinned at the girls and thought about it. "I have an idea. The one of you, who makes me come gets a little price."

The three girls made big eyes and almost fought about who was the first to suck off Jim. The game went on for several minutes, the girls giving each other some time for sucking before pulling each other's heads off his cock. At some point one of the girls had the bad luck that another guy came into the bathroom and facefucked her a bit, all while her two friends could work their tongued over Jim's cock.
Finally the second of the three, was giving everything and Jim released a huge load of cum down her throat and shoot some more all over her face. She grinned to her friends.

"I won," she stated and the other two looked a little bit pissed.

"You cheated," one of the others said. "You were using your hand to massage his balls while sucking him off."

"Nobody ever said we can't do that," she said and showed her friend her tongue. "So, what is my price?" she then asked in Jim's direction.

Jim smiled and waved the wand, letting the girl's chest grow to a nice D cup.

"Wohoo, that is a cool price," she said happy and bounced a bit, making her new tits jiggle up and down.

Jim grinned and stepped out of the bathroom again, ready for some more mischief with the people working or visiting the mall. He could hear the girls argue a bit but that was quickly muffled by all three getting new cocks to blow.