I use and have used for about 10 years on mine and my client machines and screens, keyboards and cases a product called "Sprayway Glass Cleaner" It is Ammonia Free so it is safe for the screens and other sensitive items. Spray on lint free cloth then whip on item to clean.
Never use chemicals on your iPad or any electronic devices, the chemical will strip away the protective coating and will ultimately damage your screen. Instead use a microfiber cleaning cloth like the ones sold at kbcloth.info and slightly wet it and wipe your iPad screen clean. Make sure that the cloth is only damp and not wet. This is the best way to clean your iPad.