I'd go ENTP for Mac, ESTP (or ISTP) for Edahn, Ivy perhaps an ISFJ (as she was originally typed.. it's toughest though). Myself.. welll.. NT's usually tell me I am NF, and NFs that I am NT. So, that just confirms the trend.
The trend being "Geoff can't type people for shit."
Mostly me. I'm not even close to having Sensor qualities. Not that I think it's bad, but I spend my entire life in my head. My language tends towards the abstract, and I love theory and debate. The rest works, but the S... *bzzzzzzzz*
Mac: xNTP I'd say INTP that likes people more than most and has learned to extravert over time.
Edahn: xNxP More feeling and extraversion than a lot of INTPs, but doesn't read like an ENTP or ENFP to me. Interested in spiritual things, which automatically makes people rule him out as a T unnecessarily. Ts can be spiritual, they just approach it a bit differently.
Geoff: INtP In conversations with Geoff, I read him as an INTP, but one that is pretty balanced on the F/T scale. He doesn't have strong use of either Fe or Fi, though, IMO. I definitely see him as Ne/Ti primary.
Ivy: INfj Or INtp. I think Ivy's an N that is just a bit more grounded than most. My roommate is a lot like that, and she's hard to type, as well. The F/T and P/J components seem pretty balanced, so it's hard to know which way to lean. My gut feeling is that she's actually a P that has learned life is a bit easier for one if one makes oneself DO stuff, instead of sitting around philosophizing. I think she's a practical P, if that makes sense. I think Ivy's the hardest to pin down, type-wise.