I recommend buying them Melatonin. I started using it 3 weeks ago. I get sleepy soon after taking 2 and I have a great sleep. I don't wake up with that lingering tiredness that something like, say, Panadol Night, does. The pharmacy opposite Carrefour in Villagio definitely has it for about QR36 and I'm sure you'll find it at other pharmacies (no prescription needed of course).

Best of luck!