what about NZ? flights can be quite cheap, it's easy to drive around & there are lots of accommodation options. there's a variety of things to do - mountains, beaches etc and the distances aren't huge for driving with two young children.

or you could go to tassie & do a similar sort of thing.

what about somewhere like fiji? you can often get special deals on flights + accommodation

i've always wanted to go up to the daintree & stay in the rainforest, that would be relaxing & different. i think some of them cater towards families as well.