Can I upgrade iOS and still retain *everything*, if I didn't authorize Apple ID and didn'nor had I performed a manual backup?

Question

I am an IT guy here helping 10+ iPad and iPhone users upgrading to iOS 5.  I have finished the first two devices, by the following steps:
Obtain the user's Apple ID and password
Get to a clean computer (precisely, logon to a clean profile)
Authorize the user's ID in iTunes
Transfer purchases (then it will download all installed apps)
Maannuly perform a backup (1), just in case.
Perform iOS5 update following the standard procedure.
Then during the process, iTunes backs up the device again (I am not sure if this backup (2) has any different from the one that I've done manually), but after everything is done, all apps with their data, account setting, camera roll, even the placing of app icons seemed to be restored to the updated device 100% successfully.
Deauthorize Apple ID.  "Next one please."
THAT WAS VERY TIME CONSUMING!!
My question is, what will happen if I upgrade a device without doing step 1 through 5 first ?  Will backup (2) still backs up everything and restore it,although the user's ID was not authorized in this copy of iTunes?
If this works then it wil save me a lot of time.  I can't risk to test it because if it doesn't work, I won't have a good backup to restore the user's data.
(PS) If you asked me why don't I do this on each user's computer?  The reason is because some of them do not have a computer, and for those who does have computer, most of them do not have iTunes installed.

Answer 1

In summary, there is no way, for me to fully restore all apps that my users had installed (purchased / free), without authorizing their Apple ID's to iTunes on the computer which I am using to perform the iOS upgrade for them ?
However, I found out it is possible that my nightmare will end after all devices get upgraded to iOS5. Through some tests that I did, I found an interesting fact:
- Backup to iTunes:
You need to authorize every single Apple ID on iTunes, so it can back up apps and restore for you.
- Backup to iCloud:
Since there is no action of authorizing, it will backup and restore all of your apps, whcih were installed by different Apple ID, or totally different than the ID of iCloud account. 
*I tested this scenario by backing up a device with only 2 apps installed by 2 diffrent Apple ID's (of course, one of them is used as iCloud account to back up), this device has never been connected to iTunes on a computer, I performed a backup to cloud, wipe the device, restore from the cloud, and both apps, purchased by different Apple ID's, were restored!
But I need to run more tests and confirm that it works.