The darkest Sydney skies I have seen have been out at the ASNSW 'local observatory' (also known as Crago observatory) at Bowen Mountain, just NW of Richmond. While you won't be able to use the clubs observatory (you need to be a member and do an accreditation programme) I'm sure that you would be more than welcome to share the dark skies. There is a link on the ASNSW web page including a map if you are interested:
http://www.asnsw.com/