My son started ice skating when he was 4 and is now playing hockey at 5. He's already super excited about snowboarding but I decided to start him off on skis instead since I feel it'd be very easy for him to transition from skating to skiing versus to snowboarding.
Personally, I started ice skating at maybe 8 years old. Then skateboarding seriously at 13 or so. Transitioned to snowboarding naturally by 18. Now pretty much just ski since I find it more relaxing! Anyway, my son's 5 now and we're starting skiing this season with him. Needless to say, we're all pretty excited!