We'll be staying at the Radisson in the CBD & want to find a spot to view the uncoming early New Year's Eve fireworks show & also have a nice casual dinner. Understand it will be crowded but hop some locals can advise us. Any advice is welcomed!

Here's a link which will show you the best vantage points:
http://www.cityofsydney.nsw.gov.au/nye/VantagePoints

If you're at the Radisson on Spring/Pitt Streets, you could just walk down to (1) The Botanic Gardens (2)the park near the Quay or further west past "The Rocks" ... provided you go early. NYE's pretty insane around the Bridge/SOH and I think you'll find you either eat out OR have a prime vantage spot for the fireworks unless you luck a reservation somewhere along the foreshore. If it were me, I'd pack a picnic, nice bottle of something cold (Radisson will probably make a hamper for you if you ask sweetly in advance ).... and head off with a rug to spend the afternoon in the Botanic Gardens/Mrs. Macquarie's Chair.

...and if the Radisson doesn't run to a hamper, David Jones Food Hall is next door to heaven!

margo_oz is on the money - the DJs food hall is excellent... they're cheese place is great and make sure you try the chocolate coated strawberries, they are delicious. you could easily get yourself a lovely hamper here (conveniently, there's also a bottle shop down there as well). top idea.

Try also Mcmahon's Point