We've been twice now The first when D was 5, but I think he would have enjoyed it at 3 as well.
The first time, we did the Zoo/ Safari and Circus. The zoo and the safari are very similar to Singapore. It's not as well maintained, and the animals do look a bit thin, but overall, we enjoyed feeding them and the white tiger shows.
The Circus was definitely the highlight of the trip. It's more or less a Cirque De Soleil copy. The Russian and Chinese acrobats were amazing and the clowns hilarious. D was ROFL.
We went again last month. This time we did the Amusement Park, Waterpark and Circus. The queues were long, and also the queue jumping and spitting is annoying, but we still had fun. There were quite a few rides, D is still too young for, you need to be 130cm. He loved the waterslides. And would have gone over and over, if it wasn't for the queue.
We went to the Circus again. They oversold it and we couldn't get a seat and sat on the steps. Would recommend getting there by 7pm.