2 MACs, one iTunes account, syncing apps

Hi,
Just bought a MBAir. Want to keep Mini (and big screen) for videos/music.
My setup is one iTunes library (&one account), Mini, MBA, iPad.
My issue is when updating apps. Perfect on MBA - which I connect to the iPad via USB to sync. Basically MBA has become main computer.
Prob is, the old Mini doesn't update the apps automatically (yes, I've selected "Install new app automatically'). I rarely use it anymore (but still need it), so I end up with too many apps to update (which have already been updated on the MBA/iPad) manually - and for the second time.

Any suggestions?
Thanks!

Not sure what the problem is, that's how it works. Each desktop/laptop has to download the updates independently to have the latest in the system, then when the iPad is connected, it checks to see if anything on the iPad is older that what it has downloaded and updates as needed. Downloading to the MBA does NOT update the Mini, and vice versa. Nor does the iPad update either of them, unless you purchase something on the iPad directly and then later connect, in which case iTunes prompts to see if you want to add the purchase to the MBA or Mini.

EDIT: The only way I can think of to avoid double downloads is to have a shared library on a drive that is external to both the MBA and Mini, but then your iTunes won't be available when you take the MBA anywhere outside your local network. And if you have two libraries, one on the external and one internal to the MBA, you'll still need to download updates to each, so it's still two downloads. That's just how iTunes works. I have four machines and have to download to each.

Thanks Jake. All I wanted was, when I update the apps on the MBA iTunes, those apps would update automatically on the Mini (Everything's good with the iPad - will sync only with MBA)
Simple issue, or so it seems. But difficult solution. I don't want anything external.
Guess, we'll have to update a lot of apps manually on the Mini whenever we use it. I thought that occasionally backing up the iPad with the Mini after updating and syncing with MBA would do it. Did not.

Yep, I wish there was an easy way to do that, too. But not as far as I can find.