Hamilton Island! Perfect do nothing or as much as you want holiday! Awesome for children, super safe, gorgeous, a world of it's own.. I lived and worked there for 6 months and have been back for a few holidays, last one was in March - Where we conceived this bub in fact! We stayed in private accom for 5 nights for under $1000.. It can get exxy especially if you go through the top advertised mainstream companies but I know a few cheaper (but still luxurious!) avenues so hit me up if you need info...

It's magical up there. There's a kids club as well, you have full access to every resort pool on the island, the restaurant and dining options are amazing (we also got Coles online delivered to our self contained apartment and cooked a few nights to keep costs down) the atmosphere is relaxed and totally holiday mode everywhere you go, that's their only industry so it's all tailored for having a good time.. Very much a place you can be super busy doing activities or super busy doing nothing and be equally entertained...

I've travelled a fair bit and just love Hammo!!

Other than that I'd suggest Gold Coast if you haven't been much before, Byron Bay, Cairns or Port Douglas for anywhere up QLD way and for a mini break off shore, a P&O Cruise, Fiji or Vanuatu.. All safe, great for kids and very much geared for the kind of Holiday it sounds you want...

Have fun!!!