The Melbourne Star is a great attraction for anyone of all ages. Not for those with a fear of heights, but if you can deal with it for the hour, it is 100% worth it for the experience. You truly get to see the entire city from up above, beautiful panoramic view of Melbourne. A bit slow to get to the top but a worthwhile view for sure. A great attraction for tourists as well as families with young children, or just anyone who wants to see Melbourne in a different light. Tickets are not insanely expensive, what you would expect for a typical attraction, might be considered a bit steep for that but it depends what your price range is.
Also, the Star is located in the Docklands with lots of food places nearby, so making a day trip is a good idea. There are often other festivals or attractions around the Star so again, it's a great place to take the kids.