But if you've got the kids driving would be more suited. Way quicker and easier. I wouldn't take mine on a bus everyday. We have our son at childcare in the hills (Hahndorf) so don't have to worry.
Parking fees are about $15 per day early bird. My husband has a paid carpark through his work which we use. Can you negotiate that?
A final option would be to drive to the bottom of the freeway and get a bus into city. Might be quicker and you wouldn't pay parking. 15 minutes or so on the bus from there.
You could just trial and see what works for you.