You're not really too far from anywhere on the sunshine coast. I love the Coolum/Perigian, Noosa area as it's quiet and not very commercial but still close enough to drive to see lots of things.
A drive up to the hinterland - Maleny, Montville, etc is definitely worth it. Pack a picnic lunch for the fam and stop on the side of the road overlooking the scenery. The Eumundi markets are well worth a look too - lots of great food and the people watching is well worth it! The national park in the Noosa area has some great walks too.
For retail therapy, Maroochy has great shopping centres.
Another thing I enjoy is going the the airport - Mudjimba which is just over the maroochy river towards coolum. I love watching the big planes coming in and leaving and might be something to entertain kids for a while!
I don't think it will be too cold for lovely walks and picnics on the beach either.