the pricing depends on two things, one being demand and the other the local market and competition.
Look around and see what other trainers in your area are doing for comparable classes. If you are unique and have already a list of people who want to participate, you may be able to charge a little more. Do you plan to run this as a course with a start and end date? Or will it be ongoing with people coming and going as they want to? A course tends to be lower priced per session because people make an upfront commitment.
Hope this helps.
It all comes down as to how much you want to make from this class. Demand and competition are always important to keep in mind when offering services, but if your class will be something unique than you have more flexibility as to what you can charge.
Is this a class that will be held during the snow months outdoors or is it training that targets muscles and conditioning required to help your clients to perform at a higher level when participating in winter events? This can also play an important part as to how much you can charge.