I'd say spend a day getting foley audio to layer over your footage when you are editing. If you have an iPhone it will work perfectly. Basically just go up to features and get sounds of people going off of jumps and landing and rails and stuff. I haven't specifically recorded skiing with foley audio, but this year I have been taking audio from other clips to use it with clips I don't have good audio for.
The intro segment to this film was filmed first, then I went back with just my iPhone and the Voice Memos app to capture all the sound, and unless you knew that I'd doubt you'd recognize it. Also, all of the interviews were done with the interviewees literally holding my iPhone in their hand below the frame...
This video has audio with 90% of the sounds taken from other shots, though I was shooting WITH a RODE (however, ALL of the takeoff sounds were taken from shots last year straight out of the camera's mic)
