I registered my 2ipads, how can I list them as stolen?

Stolen iPad Database

http://www.stolenlostfound.org/online-stolen-ipad-database

Also do a search, using the serial number, on your local Craig’s List. Some users list the serial number of a stolen iPad to thwart the sale of a stolen device.

If the iPad was running iOS 7, the thief/finder will not ever be able to use it.

iCloud: Find My iPhone Activation Lock in iOS 7

http://support.apple.com/kb/HT5818

Apple (and no one else) can not assist (with serial number or iCloud) in finding a lost or stolen iPad.

Report to police along with serial number. Change all your passwords.

These links may be helpful.

How to Track and Report Stolen iPad

http://www.ipadastic.com/tutorials/how-to-track-and-report-stolen-ipad

Reporting a lost or stolen Apple product

http://support.apple.com/kb/ht2526

What to do if your iOS device is lost or stolen

http://support.apple.com/kb/HT5668

iCloud: Locate your device on a map

http://support.apple.com/kb/PH2698

iCloud: Lost Mode - Lock and Trace

http://support.apple.com/kb/PH2700

iCloud: Remotely Erase your device

http://support.apple.com/kb/PH2701

Report Stolen iPad Tips and iPad Theft Prevention

http://www.stolen-property.com/report-stolen-ipad.php

General steps to follow for a Stolen iPad

http://stolen-ipad.com/

How to recover a lost or stolen iPad

http://ipadhelp.com/ipad-help/how-to-recover-a-lost-or-stolen-ipad/

How to Find a Stolen iPad

http://www.ehow.com/how_7586429_stolen-ipad.html

What NOT to do if your iPhone or iPad is lost or stolen

http://www.tomahaiku.com/what-not-to-do-if-your-iphone-or-ipad-lost-or-stolen/

Apple Product Lost or Stolen

http://sites.google.com/site/appleclubfhs/support/advice-and-articles/lost-or-st Len

Oops! iForgot My New iPad On the Plane; Now What?

http://online.wsj.com/article/SB10001424052702303459004577362194012634000.html

If you don't know your lost/stolen iPad's serial number, use the instructions below. The S/N is also on the iPad's box.

How to Find Your iPad Serial Number

http://www.ipadastic.com/tutorials/how-to-find-your-ipad-serial-number

iOS: How to find the serial number, IMEI, MEID, CDN, and ICCID number

http://support.apple.com/kb/HT4061

 Cheers, Tom 😉