My experience with our now four-year old is that he is interested in almost everything, cause everything is new to him. While Tainan’s history sounds kind of boring, it probably is not. The Anping Canal cruise is kind of fun, also visiting the warship museum. They did have Snoopy images there recently not sure if it’s still the case. Also Yuguang Island has a good beach with cool sunsets.
https://historic.tainan.gov.tw/index.php?option=module&lang=en&task=pageinfo&id=166&index=1
