The Cracker is indoors and mainly carpet with jumps & bumps. There are often a few slippery corners. Yellow Mini Pins are a safe bet on 4wd buggies, dunno on SC - I'm sure a regular SC runner will be along shortly to add some suggestions.
Heres a short vid showing some racing from a few years ago - it gives a decent impression of the venue and surface (pitting in in another room).
http://www.youtube.com/watch?v=ul-aHGYRH2o
HTH