Upvote:3
Japanese citizens are among the few people who can visit China without requiring a visa. Japanese citizens can visit for tourism or business purposes without a visa for up to 15 days, so you're all set. You do not even need to use TWoV if you hold Japanese passports.
Pandas: no, I'm afraid not. Pandas aren't that common at all in China, and few zoos actually have pandas, and I am quite sure there's max 1 zoo per city. You'd have a better time if you save it until you return to Japan, acutally :-)
Taxis are fine as long as you can communicate with the driver. Subway is also fine, but crowded.