J.A.
My DS started Parent and Child Ice Skating at 2 1/2. He LOVED going during the hot summer months. The rink we went to was about $11 per lesson (Pretty sure it was $110 for 10 weeks) and that included once a week lessons, once a week free skate session(twice if you stayed on day of lesson) and skate rental for both of us.
Now he wants to learn gymnastics and T-ball. We are looking into prices for those. We also plan to put him in swim lessons this year. (He will be 3 1/2 this Summer.)
So- my answer is if he is intrested in something and you can afford to help him embrass it, GO FOR IT! At this young age, never force a "hobby" on them. They will show intrest in the things they really like doing. Even if he is an arts and crafts boy, let him explore the intrests! He will be no worse off for trying something that is a bit boring once or twice, but he (and you) could discover he has a passion for something that will become his drive.