Yeah, the original 3 always have a chance of coming back. And it's also possible for one of the other randomly generated names to come up again, though it would technically be a different Kerbal (probably with different stats).
Fortunately, if you want EVA science points for the "flying over [X]" portion of each biome, you can do it from the ladder of a landed craft rather than trying to hang on while actually flying.
I've been making an "easy" run through the science tree. Not trying to Scott Manley it by building an amazing machine that can tour the entire Kerbal system on the 2nd flight for over 6000 science points. For example, for my first mission, I just put a plain capsule on the landing pad and got 29.9 Science from it. First flight was just capsule/tank/engine, and got a bunch more, etc. Even my interplanetary probes were a far cry from the multi-orange-tanked monsters I've been using to huck my space station parts into orbit.
And because I've been taking copious notes on how the system works, I think I'm going to try my hand at a video tutorial/guide on the subject. I've seen a lot of good info from my usual round of KSP YouTubers, but nothing that quite puts it all together in a way the average player could use to successfully climb the tech tree without ridiculously heroic efforts. In particular, there are several aspects of it that if you don't understand, can get you bottlenecked pretty quickly, making it all more frustrating than it needs to be.