Since there are no enemy villages on the map, you don't need to fear an attack, and you can take your time. Build up your base until you can train Stone Throwers. Build Light Transports, and send the stone throwers over with a few soldiers. Use the stone throwers to destroy the enemy Watch Towers and the soldiers to kill the animals (Lions and Alligators) that could threaten your Villagers. Then, send a few villagers across, to gather the stone and build the buildings to complete the mission.