The skyrail is in Kuranda, so if its open and you have the time to get to it, its 100% worth checking out.

LeojVS mentioned the harbour bridge climb, its a bit pricey, but you really should do it if you can. Its not a particularily difficult climb so you should be ok with it. Do it just to say you've done it!

Sydney has an awesome mix of food from all over the world. To be honest I'd steer clear of eating roo and the like. Its ok but its never going to be as good as you'll get out in the bush for example at Ayers Rock (Uluru). The one restaurant a lot of people want to go to is Doyles. Supposed to be some great seafood there, so good to look at.

You can also take the ferry to Manly beach for the day from Sydney. Its a nice ride and there are plenty of 'touristy' type things to do. Plus you get a chance to get out on the harbour which is also really nice.