Backup your iPad before you update to Lion. Although I don’t remember reading a specific article about this, if you are about to update to Lion on your Mac, you should sync your iOS device with iTunes, then make a bootable back up of your hard drive (A product like Carbon Copy Cloner may be good for you.).
Apple has several articles about iPad backups. This one is helpful. In part, it states:
iTunes can create backups of settings and certain other information on iPad. You can use a backup to restore this information to your iPad after a software restore or update, or to transfer information to a different device.
You can create backups in the following ways:
If you have configured your iPad to sync automatically with iTunes on a specific computer, iTunes will back up the iPad after you connect it to that computer and sync with iTunes. iTunes will not automatically back up an iPad that is not configured to sync with that computer. iTunes makes only one backup each time you connect, even if you sync multiple times before disconnecting.
If you protect your iPad with a passcode, you will be prompted to enter the passcode when you connect to iTunes. Once you enter the passcode successfully, iTunes will recognize that device as authorized and you will not require your passcode to back up or sync.
If you do not have your iPad sync automatically when connected, iTunes will create a backup when you choose to sync.
Right-click (or Control-click) the iPad in iTunes under Devices and choose Back Up.
If you choose to update the software, iTunes will back up the iPad automatically.
If you choose to restore the software to factory settings, iTunes will ask you if you want to back up the iPad.
After restoring your iPad software to factory settings, iTunes will show a Set Up Your iPad screen. If you choose to “Restore from the back up of”, iTunes makes a copy of the backup you chose to restore from and that copy is marked in the syncing preferences of iTunes with the data and time when the backup was created.
So, before jumping into Lion, don’t forget to sync your iOS devices with iTunes and make a back up, just in case.