Rockhampton is a mining town, and there really isn't all that much to do there. From there it's a short flight to Townsville & Cairns to the north, various islands and resorts on the Great Barrier Reef to the north & east and it's only a 3 hour flight to Sydney if you want to go power-shopping.
If you're going to be there over summer, why not spend some time at the Whitsundays? They're a group of islands on the reef that have amazing diving, snorkling, sailing, etc etc etc. The resorts on the islands and on the Daintree are also really nice, especially the more high-end ones that don't cater to children - cocktails on the beach!
Rockhampton seems an odd place for military training - Townsville is the army town (very big base up there), and Cairns is a navy town. Unless he's doing excercises in Shoalwater, in which case my husband will probably be mock-bombing him.