First camp would be a newer AV receiver, with zone 2 and iPod dock included. Drawbacks are, you will likely need to use some sort of IR blaster to extend your main remote capabilities so you can control the receiver from outside (e.g. switch radio stations). Most docks are meant only for controlling the iPod. OTOH though, there *may* be a higher priced AV receiver that allows you to control some functions via an iPod app. More on that later. Another issue is whether or not the included cable with the iPod dock is long enough to reach all the way to your outside area. YMMV. If the outside space was just outside, perhaps running it through a wall to ad adjacent outdoor shelf wouldn't be impossible.

Second camp may be as follows. AV receiver with zone 2. iPod dock/speakers & separate outdoor speaker pair that can connect to the AV receiver inside (via 'B' or A/B speaker selector switch). IR blaster to access receiver functionality from outside. Send radio source outside via 'B' speakers; play iPod music on separate iPod dock/speakers when desired. I like this a little since you also can remove/relocate/travel with this distinct iPod dock/speaker device. A second set of speakers for your outdoor area is also a very nominal expense, which works in your favor to put a little extra money toward getting the dock you really want/like ;).

Other ideas-

Quite possibly you could opt for something slightly different but equally as functional (at least in the same general wheelhouse, if I get the 'gist' of what you are after). You could grab nearly any AV receiver with digital optical inputs (even older ones can suffice), and utilize an iPod to stream your music wirelessly to an Apple Airport Express Base Station. The sound quality is quite good IME, and you also get additional options of being able to stream other content over your wireless network with additional software. Any iPod Touch or iPhone can send streams to your airport express, which connects to nearly any AV receiver via a digital optical cable.

More in the proprietary vein, you could see if any updated AV controller iPod apps exist, such as this one from Sony-

The Onkyo app might be worth looking into as well:

This might let you control the AV receiver playback without having to deal with any sort of IR blaster (accessory that extends your infrared signal). Drawback is, it may be buggy and only work with a few models. And then there's the issue of updates(?) I'd point to the Sony as being more limited though. Onkyo is normally pretty good all around.

There may be something off the shelf for you @, if you look in their tutorial section. I also like perusing AVS forum. I normally learn something new each time I poke around their forums/reviews. Link:

Home A/V distribution sub-forum

If you have more questions, feel free to ask. One important feature of some receivers that is missed is that the zone 2 option is limited to certain types of inputs. IOW, you can't always send out two separate digital sources simultaneously, etc.