How can I re-setup an iPad 2?
You can wipe the data and return it to factory settings by choosing settings - General - Reset. 

Like the first answer you should now name them differently.

Just to add to that you will also need to restore one of them to empty, then set it up using iCloud, add iCloud to your other iPad 2 and then they will share data, but you will also be able to add an app to one and delete from the other without losing all data, next time you sync.