Yes, you can update apps in iTunes without the iPad connected. On the left side of iTunes should be a line titled "Apps" (I have my iTunes set-up to show that left column - like the older versions of iTunes had automatically).
Once you are in the Apps section, look for an update button at the top of the displayed apps. Clicking on it should make iTunes tell you that you have x-number of apps that need an update. You acknowledge this and then iTunes will download all the updates.
Then, once the updates are done, you should be able to connect your iPad and sync the updates over.
Hope this helps.
Marilyn