The closest island resort to Nuku’alofa, Pangaimotu makes an easy day trip. Daily departures (including Sunday) chug out from the wharf beside the Fish Market at 11am, returning at 4pm (Sundays departing hourly 10am to 1pm, returning 4pm, 5pm and 6pm). The trip takes about 10 minutes. There’s a decent beach, a good restaurant and shipwreck snorkelling – bring the kids!
If you want to stay the night, Pangaimotu Island Resort has simple fale (doubles from T$100).