Hi girls, congrats on your pregnancy!!
We used an anon sperm donor through Melbourne IVF so Charlie's birth certificate has a blank space for the father ( hopefully with my name on it one day when the laws change..... ) and in Vic you can put any last name you want, not necessarily only the name of the birth Mum. We lodged it with both our last names as a hyphen and it was accepted no problems at all.
To us though, it is just a piece of paper and hopefully by the time he is old enough to want to read it, he will be secure in the knowledge of who his parents are.....
so it won't matter who's names are on there