Are many venues open over the Christmas/New Year period?

I am from overseas and my family can pretty much only come to Australia June-August or around Christmas. We're wanting a wedding in Newcastle so are worried about the weather June-August being cold, wet, windy and not a great time for people to explore Australia at its best. This pretty much leaves the Christmas period. Of course this is subject to availability of venues but I wonder if generally they all close down or stay open over that period. Thanks!