I wouldn't worry about slotted rotors cracking unless you're doing some serious heat cycles on them and getting them glowing hot. I've heard some pretty mixed reviews on hawk pads, some people say they are great track pads, other say they are worse them the OEM pads (for s2000's).

Anyway, unless you're doing multiple hard stops without much time in between, I'd just go with the flats. And get pads that have reviews of having very good cold bite. Because chances are you won't have them hot when you need to use them.