I take my two year old to OP 2-3times a month since it's close by. If you go, woud advise you to do go early, like 10am when it opens.,,do the aquarium, panda and then kiddy rides, then venture on the train to the other side. There you can have an early lunch and then come back on the cable car, on returning, you can stroll through "old HK street" which is fascinating for kids and adults alike. By doing that you avoid the ling queues for the train/cable car. It's fun!