Good question. I was concerned about that as well. I have taken (and continue to take) all of the dental school pre-reqs in person at the local state university. Both parts of this statement are important: online learning doesn't hold a candle to in-person in the eyes of an ADCOM and they don't want to see community colleges (unless you have a seriously good story for why you took them there and you've followed up with upper-division science classes at a 4 yr college or university).
As for everything else, I've taken almost all of it online. For example, last semester I took an online histology course through the local community college. It was just a single credit and it required me to memorize a myriad of cell types and structures, things I'd need to know anyway. More importantly, it was an easy boost to my science GPA. If your schedule can support you taking exclusively in-person classes, then by all means go for it. If not, online classes are not the devil (as some students here would make it seem). I will caveat that though: when in doubt, call the schools you are interested in. At the end of the day, it's what the school wants that matters.
As for easy or hard because I'm active? Personally, I think it's been incredibly easy. Sure, I have to work hard and study to get the As I've been earning, but I developed an excellent work ethic while in the Army. I'm going to assume I'm a lot older than you, but the age difference between me and my 18-20 year old peers has also not been an issue. My lab partners have been great and when I say what I want to do, they never disagree! (Not sure if that's because I seem intimidating and they don't want to tell the old Army chick "no," but it's worked for me so far!
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