It is worth driving up to Sky High just for the view alone. You need to pay $5 for car entry, but this is for maintenance and upkeep of the grounds. The view itself is spectacular, especially if you are lucky enough to be up there on a clear day.
We have eaten at the restaurant several times, but most recently for our wedding anniversary. It was lovely sitting by the window watching the sunset over Melbourne, then the beautiful twinkling lights beneath us. The food itself was pretty good, thoroughly enjoyable. We had three courses, and shared the chocolate fondant (gorgeous).
I recommend coming during the day if you come with children, there is a giant's chair and a maze to entertain them. There is also a lovely garden to stroll through.