Heterosexual pedophiles are far more common than non-heterosexual pedophiles.
Compared to the general population, the percentage of pedophiles who are homosexual is higher than the overall percentage of homosexuals (which is much higher than 5%), though. The main reason for that is the pretty much universal phenomena that anyone with one social deviance is more likely to have others. In reality, the reason for that is probably not that they're more likely to be deviant, but that they're less likely to hide it and are more likely to be open-minded about other deviances.
You're also conflating different things though. Pedophilia is not the same as child molestation. Pedophiles are only slightly more likely than non-pedophiles to molest children. And considering pedophiles are the minority, that means most child molesters are non-pedophiles.
I think the biggest factor by far is opportunity. Men are generally able to spend more time alone with boys than with girls, it's acceptable for them to be naked together (locker rooms and such), and they have more chances to do sexual things with them. Boys are somewhat more eager for sex than girls are too (though the difference is smaller than a lot of people think), so that also makes it easier.
Also, don't forget that women can be pedophiles too, it might even be more common than men. But people don't really think about it and it's barely studied at all.