I've only been to Tioman (flying) and Desaru (which is disappointing), but people always say that if you drive on further north than Desaru it gets much nicer along that coast (I'm presuming they don't mean driving as far as the boat to Redang

).
We've been to Tanjung Resang a few times. It's lovely, quite secluded, no crowds. And it's surrounded by pristine terrain, both jungle and beaches. The beaches are a bit rugged but awesome for long lazy strolls.
There's a little hill just behind the main compound there, Gunung Arong, that's ideal for a recreational hike.
The food is great, the accommodation is basic but clean and cheap. All in all, an ideal place for a family weekend away.