I want to start out by saying that being a repeat cheat doesn't mean someone is a sex addict. There is SO much more than just sexual infidelity to sexual addiction.
That being said, I don't think ANY addict, be it sex, drugs, booze or whatever, is a good parent if they are active in their addition/acting out. An addict will ignore & hurt everything else in their life to get their fix, including children.
Having said THAT, the court doesn't care if a parent is a SA when it comes to deciding custody & visitation. The only way the court will care is if the SA has already molested the children or has had them in the car/the house when being serviced by a prostitute or having a swinger/S&M party. Most addicts don't have sexual tastes that run to the pedophilia/hebephilia side of things, BTW.
Finally, and this is the hardest pill to swallow, if one's spouse is an addict it is most likely that you have some dysfunctional coping skills already, too. So if your kids haven't internalized the addict's mental & behavioral poison, they've internalized yours. When you live with an addict, the damage is already done.