I also am a 42 year old single mum with a 7 year old and a 2 year old, living in Melbourne. It's tough, running around with a two year old. I've chosen to be a stay at home mum at the moment as I also have little support and want to be there for my children. The children's father is absent so I do not get weekend breaks too. Once they start school, it does get a little easier.
Let me know if you want to chat.