My DD4 was 16 months when we went, it was fun, she got all dressed up. I was surprised by how well she did as we went the night we arrived. I expected her to be tired, but since she slept on the plane and in the car, I guess she had some extra zip in her. We went on quite a few rides, she fell asleep in my lap on two but we kept going. She wasn't much of a sleeper anyway, so she was pretty wide-eyed until at least 10:30 or 11. She was a bit drowsy our last hour there, but she did make until we were on the bus.
I really think it's geared towards all ages, everyone had a good time. There's lots of candy and short ride lines for the older kids, and lots of characers in their halloween costumes for the younger kids. My DD really wasn't scared, she more just looked up at everything in amazement. I can imagine a 2yo being more frightened though, even my then 11yo kept waking up with nightmares

(yes, that confuses me too, I guess she kept dreaming something about bats). The only thing that I found that could be considered scary was the parade, a few of the villains imparticular. If your worried about it, just skip the parade, the bonus of that also is that lines are shorter. Most of the party is just cute, Main Street is much more festive than spooky.
I reccomend going, it is a lot of fun, I think he'd enjoy getting dressed up and seeing the characters.