With only the information you have given, I think refusing to allow him to come to your house or refusing to go to his house are not the right moves, for a variety of reasons:
People can make mistakes, and also people can change. Even supposing that at the time this crime occurred he was 100% guilty, that doesn't mean he will commit a similar crime in the future.
The crime he may or may not have committed is different than the crime you are supposedly trying to protect your daughters from. Hiring a prostitute is not the same as molesting/sexually abusing/raping someone.
The way your story says "it was suggested that an underage girl (16) was available". First of all, who was the one doing the suggesting? Was it a cop? If so it sounds to me like they were purposefully trying to push that on him in order to charge him with it. Supposing it was a pimp suggesting it? Still, the way you tell the story makes it sound like he didn't seek out/ask for an underage girl, it was pushed on him.
In some places, both in the US and around the world, 16 years old is considered old enough to consent. As he was charged with a crime, it is obviously not considered legally old enough to consent where you live. Still, regardless of the law, it sounds like he was trying to pay to have sex with a consenting individual.
All that being said, I'm just trying to play devil's advocate. I don't have his side of the story, and even with your side of the story I feel like there is some missing information. I am just going off what you said. For all I know he is a scum bag child molesting pedofile who you should try to protect your daughter's from. But also for all I know from what you have said, he might be a normal guy who would never hurt your daughters.