G'day Aurora,
If you head up to Lamington National Park to O'Reilly's there are heaps of 1 day circuits you can do, very scenic. The drive from Canungra up to O'Reilly's does take 1 hour though.
You can drive up to Binna Burra (from Narang) and do more Queensland Alpine Circuits there too.
If you head north to Kondililla Falls you can do a day hike south to Boreen Dam and back (full day hike - good training for the kids).
Further north, we have done the hike at Rainbow beach (Carlo Sandblow to Lake Poona). A nice tannin lake to swim in. That is an easy shaded 20k round trip: check out the link from the last time we went there:
http://www.everytrail.com/view_trip.php?trip_id=2674099We have an easy 4 day hike coming up in June if you are keen, my 8 year old girl is coming too:
https://www.facebook.com/#!/events/649508698430363/On how hikes we carry all the young kids' stuff (I just got a nw 80L pack to do the job). With a pack on they just can't keep up and do the 20ish Kilometres that we want to do. So they walk with a water bottle, have a great time and sleep like a log at the end of it.
Good Luck
Chris K