Alternatively, find him a kid sitter and get out on the slopes on your own. I think he will get over it, but it may just require more maturity. He is only six, as time goes on he will get better at handling his fear of things. But I totally agree with Portia, if you don't have buy-in, and a way to get out quickly if things go south, I would not push him.
My experience as a parent of a teenager is this one. Six is still fairly young for many of these activities. Even though other kids do it. My experience is often that starting really young turns them off an activity rather than on, I did this with swim team. Really wish I had waiting to introduce my DS till he was 8 or 9 rather than 5. Go skiing as a family and find him a babysitter or put him in the onsite daycare. Expose him but don't push. And you will be surprised in a few years he may be very happy to joining you.
