only a 30-45 minute drive away from the Gold Coast lies Purlingbrook Falls, in Springbrook National Park. These waterfalls are an amazing site, and I certainly recommend taking the hike down to the bottom. You will need 1.5 hours up your sleeve to get down there and back up, but certainly worth the effort. The falls are certainly flow better just after rain, but constantly run all year around no matter what the conditions.
The drive will take you up into the Gold Coast Hinterland, and it is a fair climb up to the top. The road can get quite twisty in some parts. Certainly well worth a family trip up there, and make sure you take your camera.