Nice one!
Really a nice one. In fact it anything you need for a good flash toon: nice look, nice characters, nice music (which was quite good by the way. Done by you brother, right? Good job), nice sounds, nice animations and a nice little story.
Although there were camera angles I didn't liked, like the one in the last scene, where they skid down the slope with the loops, but it was okay and didn*t spoil the Animation. Just a little suggestion, how you could have made the last scene better. Just imagine that the camera looks down that slope, with it's loops and the end of the track in the center of view. Then you see all the Characters skidding by the camera, maybe over a little snowmound in the foreground, just to disappear and then again they appear again a little further down the track, where they get samaller and smaller and you see them enter the first loop and the second loop. Then you cut the scene, maybe to a close up of the Yetis face,; The Yeti is having fun but suddenly he changes the expression to a surprised one. Then you bring the camera to the whole scene, where you can see, that the Yeti ran over the two little snowmen. Then they rebuild them and the scene ends either the way you did it or with the group looking at each other and the Yeti starts skidding down another slope, right into the direction of the camera. When he reaches the Camera the screen goes black and the credits appear.
I hope, that this was of a little help. Playing with the camera can add a whole lot of quality to your animation. Also the use of focus.
So on the Whole, it's a really good toon and your efforts were not in vain.
So go on, and give bring us some more stuff. Maybe even from the Yeti, since it could make a good lead character for a series.
Keep it coming!