I don't eat Chinese food so I can't comment on China Town for food but there's The Gate not far away from there which has the usual Frankie & Benny's, Pizza Hut, etc... sort of chains (probably not suitable for any younger family members later at night as there's loads of bars in there too - it's conveniently near the camera shops though). There's some nice restaurants down Grey Street past the theatre and a fair few good ones down by the train station and Centre For Life (outdoor ice rink there if you fancy a go). If you're stuck for food ideas, tourist info is at the bottom of Central Arcade and should be able to help.
Someone else mentioned St Mary's being lit up at night. Hasn't been the past few times I've been there but it's still worth a trip for photos - especially if you time it right with the tide.