Well, my middle DS was 16 months his first trip and 28 months his second. Is that a close enough comparison?
When he was younger, he did very well with character meals that had mostly face characters (so princesses, 1900 PF, etc.) and CP ... he has always loved Pooh and the Gang. The other non-talking characters scared him a bit with the exception of another fave, Garden Grill, but he was over that by his second trip. At GG, the characters worked to overcome his hesitation and the restaurant also revolves which is an added bonus for keeping them interested.
He loves Biergarten. The oompah music is so much fun and they encourage kids to dance in the center.
We had an early dinner at Kona Cafe when it wasn't too crowded and the servers were WONDERFUL with him, giving him lots of attention and distraction.
He loved HDDR. I thought he wouldn't last but he was fascinated the entire show, just gnawing on a piece of corn most of the time. (OTOH, the Luau bored him, literally, to tears)
Generally, buffets have worked best for our kids at this age. Immediate gratification!
Coral Reef had an emergency and shut down while we were waiting to be seated. I really think the fish would be fun for little ones. We'll be testing that this month, so I can't say for sure!