If you are campers perhaps go on a longer camping or caravan trip maybe to the outback if you're into that sort of thing? Go up the centre of OZ, Uluru, mataranka hot springs, coober pedy and get an opal for your anniversary etc and camp along the way? It's a different experience though and it's not everyone's cup of tea and you'd probably want to go for longer than a week. I've also lived/worked in the Whitsundays and I found Daydream Island catered for kids the best out of all the islands. When reading your post I also thought of a cruise, have you found any good deals?