But also, said history of cheating did not occur when they were a child, but when they were a late teen or older, so there are no excuses you can find to justify or explain why they cheated at the time.
In this scenario, would knowledge of this affect you dating this person? Would you expect to be informed? And if yes, when would you expect to be informed?
Answering the question in the OP, if they were a complete stranger, I probably wouldn't even date them to begin with if I knew about it. ...Not for any specific reason other the fact that it's human nature to be judgmental and we judge people based on the information that we know about them.
I wouldn't have faulted them if I started dating them and they didn't tell me right away. It's a sensitive topic that I wouldn't expect to be brought up on a first date. However, it is a serious enough of a topic that I would expect to learn about it sooner or later, and I'm nosy enough of a person to be curious about my boyfriend's past relationships. It's just in my nature to be somewhat stalkerish.
The critical thing for me is that they don't hide their past or try to bury it with lies. The way they talk about how that incident matters a lot to me (not just the substance of what they say, but also their feelings and how they act about it). I'm not interested in hearing the nice-sounding explanation. As a matter of fact, I like to think that I'm decent at detecting bullshit ("It was a huge mistake, I regretted it immediately, I promise to never do it again I promise!"), and frankly I just want to see and understand his vulnerabilities both inside and out.
My read on the person is essentially more important than exactly what they say.
As for my own relationship with that episode of infidelity during college, I had been childhood friends with my partner since I was 7 years old... everything about that incident unfolded exactly in a way that I could see it and understand it (kind of like watching a car accident in slow motion). If anything, I knew my boyfriend (now husband) so well that I feel like I could have even predicted it given the circumstances at the time (we were in a LDR and he had just flunked out school and needed to take a gap year). It's kind of weird because I still get premonitions about our relationship even today, and I can think to myself, "If we do X, I think we'll be divorced in 10 years, so we should avoid that." I feel like I don't have any lofty ideals or preconceived beliefs about marriage or love, and nothing should ever be taken for granted... I am also not faultless and I have many of my own deep flaws. There are certainly practical elements and specific things that I want/need from my relationship, and to some extent understanding my partner better than anyone else in the entire world is a major aspect of why we got married. That... and being co-dependent... despite numerous other semi-dysfunctional aspects of an imperfect relationship. Again, I don't regret a single thing and I'm very happy how things are.