hi my ipad is disabled. my kids used an incorrect password to open it. how do I unlock it as when I connect to itunes it is not visible as well?

You will probably need to restore using Recovery Mode. You can read about it here.

http://support.apple.com/kb/ht4097

Recovery Mode Instructions

• Disconnect the USB cable from the iPad, but leave the other end of the cable connected to your computer's USB port.
• Turn off iPad: Press and hold the Sleep/Wake button for a few seconds until the red slider appears, then slide the slider. Wait for iPad to turn off.
• If you cannot turn off iPad using the slider, press and hold the Sleep/Wake and Home buttons at the same time. When the iPad turns off, release the Sleep/Wake and Home buttons.
• While pressing and holding the Home button, reconnect the USB cable to iPad. When you reconnect the USB cable, iPad should power on.
• Continue holding the Home button until you see the "Connect to iTunes" screen. When this screen appears you can release the Home button.
• If necessary, open iTunes. You should see the recovery mode alert that iTunes has detected an iPad in recovery mode.
• Use iTunes to restore iPad.

Connect in recovery mode and restore, you'll get the option to reset the passcode during this process:

iOS: Unable to update or restore and iPhone and iPod touch: Wrong passcode results in red disabled screen

If you cannot remember the passcode, you will need to restore your device using the computer with which you last synced it. This allows you to reset your passcode and resync the data from the device (or restore from a backup). If you restore on a different computer that was never synced with the device, you will be able to unlock the device for use and remove the passcode, but your data will not be present. Refer to Updating and restoring iPhone, iPad and iPod touch software.