Again – apologies. I think I’ve figured it out. Set the viewport info to the following:
<meta name=”viewport” content=”width=1200″>
This ensures the site loads perfectly (in Chrome) on both the iPads and the iPhones.
Safari still doesn’t display correctly in portrait mode (both iPads and iPhones) – but does in landscape. If you “pinch the site down” in portrait mode it automatically sizes correctly. So I think this is probably the best it’s going to get.