Hi there Jack

Welcome to the MAS.
Yes, a number of members will be down there this weekend, from Friday (tomorrow) onwards. If you turn up on Saturday after lunch there'll most certainly be people there. Ask for Ned when you get there, as he's the bloke that takes the $8 per night fee. If you plan to camp outside or stay in the cabin, there'll be room for you, no problems. I'm going to Lightning Ridge this weekend for my father in law's 60th, so I'll miss out on the forecast clear skies, but c'est la vie.
Take your thick woolies as it's very cold there at night. Take food and bedding linen or sleeping bag. There's a full kitchen with fridge, stove, cutlery and microwaves, etc. Full 240v power is available out in the middle of the viewing field, just bring a 20 meter extension cord.
Have a great time - the conditions should be great.