Meggyme

I will be doing a 15 day Celebrity cruise from Sydney with my husband, 70 year old mother in law, and my 7 and 4 year old kids. We will be stopping at Brisbane, Airlie Beach, Cairns, Darwin, Bali and ending in Singapore. My primary goal is to get my kids to see some fish at the Great Barrier Reef, but they are both new to snorkeling. Interested in any recommendations for this itinerary.