If you dont want to do anything with your degree then there is nothing wrong with that being a mum is just as important as any other career choice.

The only thing i would offer would be that it is worth finding out if there is a time limit on when you can complete your degree re hecs.
If there is seeing as you only have 4 units to go the advice that i would have is to finish them within that time limit. There are lots of things you can do with an arts degree and i've found that alot of them have nothing to do with the units youve studied. For example if youve studied english you might head towards a career that requires excellent written and vocal communication skills.