Our Langkawi itinerary was quite relaxed, not so much of rushing around to go to the next destination or the next city. We took our sweet time going from place to place, and spent some time by the pool and the beach. But if you are tight for time, I think you can still use my itinerary for a 3 days 2 nights stay. Here is our actual itinerary:
Day 1 - Arrival at Langkawi (30 minutes from Penang, 1 hour 30 minutes from KL). Lunch at Sawadee Thai Restaurant. Checked in at Sheraton Hotel.
Day 2 - Lunch at Tapaz Restaurant at Perdana Quay. Langkawi Underwater World. Kuah Town for shopping.
Day 3 - Langkawi Panorama Skycab. 7-wells waterfall.
Day 4 - Kilim Geoforest Park. Travel home.