Did you download and install iTunes 10.5 before you updated the iPad? I thought that you had to do that first, but if you didn't, that may be the reason that you don't see the option. I copied this from an earlier post for the setup instructions.
iTunes must be running. This works for any iDevice. You will be able to initiate a sync on your own after you set this up. Autosync occurs when the device is plugged into a power source, You do not have to be plugged in to start the sync on your own.
iTunes Wi-Fi Sync
- To activate syncing over Wi-Fi, plug your device into your computer and open up iTunes.
- Under the Summary tab, scroll down to the Options, then ensure Wi-Fi syncing is enabled. Your device should now sync automatically over Wi-Fi when plugged into a power source, but you can initiate a Wi-Fi sync manually using the steps below.