You possibly could pick colonists who don't need physical sexual activities or bring up families so they could have sex in the colony with each other. Using technologies and porn is also an option, although not as efficient. As the human colony grows above certain size, the sexuality problem may disappear since the humans would have enough numbers for finding mates within the colony.
So here we come to the question of jealousy in the colony. If you bring in nice people, this should not be a problem. Nice people behave in civilized way. Jealousy between nice people does not result in violence of animosity. They discuss the problems and respect choices of each other. This is possible even in human culture.