One girl has a wild-child personality and has dated guys my age (or so) before. But overall very sweet.
The other is the type who wants to reinvent herself in college. Not a party girl, or at least doesn't seem like one. Outgoing though.
Both initiated with me. Both have merits.
Any thoughts? Should I stray away? How is this perceived in general?
If the 18 year olds seem mature enough for you to enjoy their company, then why not? My concern would be more that the wild-child girl sounds flaky and might be bad to get involved with for that reason. The other one doesn't sound like she knows who she is at all right now, because she wants to reinvent herself. It all depends on what you want... just having some fun or finding someone who has potential for a real relationship.
I know lots of guys in my university who date high school girls (Some of which who were in the 10th grade!) and 18 and 21 isn't too bad considering guys are usually older anyway. Also, if you follow the half your age plus seven rule, you can date as young as 17.5
However, a high school mentality is a lot different than a University one, waiting a year would probably make a big difference if you didn't mind. Still I think it's fine. Go for it!