I say, go for it! I've been skiing since I was 5 and skied all the time when I lived in Colorado, and can say that it's very difficult to fall forward and land on your stomach with skis on. If you did fall, you would most likely land on your right or left side or on your butt. Be careful with your poles, though, because you could stick your pole into the snow in front of you and hit your stoma with the handle. As LP mentioned earlier, with all of the layers of clothing you would have on, your stoma would be well protected. It sounds like a fun trip, and I highly recommend skiing the Rockies!!