Hi Sammy,
I am om a 489 Visa in NT. Schooling is free for state school but there are schools that are fee paying. depending on the age of your children/child i would strongly recommend looking at the NAPLAN results for the schools in the area your interested in moving to. Healthcare - You are covered by NHS (Medicare reciprocal agreement) however this does not cover you like the NHS for everything, its not part of the 489 Visa conditions to have private healthcare, however having done lots of research and speaking with lots of agencies, visa holders, permanent residents etc, if hospital care was needed due to my 489 visa status i would be faced with hefty bills. I have private healthcare as i wanted to ensure that should my child need medical care she would get it no matter what and i wouldn't have to be concerned about how i was going to pay for it....
Hope this helps, it sounds very daunting but its most defiantly worth it .