Tickled pink! On Sept. 22, Bindi Irwin and husband Chandler Powell revealed the happy news that they’ll be welcoming a daughter early next year. “Baby girl, you are our world,” Irwin, 22, captioned the Sept. 22 Instagram announcement, which showed Powell, 23, holding a new sonogram picture. “They are walking on air right now,” a source tells Us. “Officially, they’re saying they didn’t have a preference on the baby’s gender, but Chandler was quietly hoping for a girl. He loves the idea of a mini-Bindi.” Meanwhile, the Aussie animal conservationist, who revealed in August that she had a bun in the oven, “is enjoying every element of this pregnancy,” the source adds. “Bindi’s got tons of energy and she and Chandler are having the time of their lives. The countdown…