I'll be there, think this is my 5th year in a row. Unfortunately this year they've changed the format and it'll be staring and ending a lot earlier
I don't know what the ground clearance in my STi is, but it can't be much more than what your mini has. And frankly, if you're worried about beating up your front bumper WCR may not be for you. People always
wind up in snowbanks and ditches, and every once in a while someone winds up parked upside down in a field.
For the first three years I just ran winter tires, but then I hit some ice... then I hit a snowbank... with a guardrail in it. So now I use studded winter tires.
If you go to dirtyimpreza.com and search threads by WhiteKnuckle you'll find my write-ups of the last several years, should give you a decent idea of what to expect.
If you do wind up going, good luck, it really is a blast.
Edit: Here's what my car looked like 2 years ago after hitting the guardrail: