Hmmm, let me think... there's the Singapore Zoo, which has lots of activities for kids and adults alike. They have these cool animal shows and even segmentation exhibits where you can see animals up close. It's really educational, with lots of signs explaining about the species too. And if you're up for it, you can also bring your son on the night safari nearby!
Or you could bring him to the Singapore Botanic Gardens, a huge outdoor space with loads of nature trails and pretty flora. There are also conducted tours that you can join, where you learn about the different plants and trees, or even discover their various uses! It's very intriguing as a parent to see what sparks our children's interest, right?