Should I get (1) a big Android phone & MacBook Air or (2) a smaller Android phone & iPad?

Keep your Nexus One, and go for a MacBook Air (11"). Why? Well, your Nexus One offers tethering if you can't find any wifi anywhere, and is perfectly capable for quickly reading email (and for short replies). Your Nexus One, with Android 2.3.3, is not redundant technology at all, and an upgrade to a bigger screen will give you nothing other than an even worse battery. You may find that a carrier-restricted new phone is less capable, and will almost certainly have an older version of Android on it. My review of the MacBook Air 11" is here: http://james.cridland.net/blog/a-month-with-a-macbook-air-11-review/ ...suffice it to say, it's an excellent machine and you won't regret it.

The choice is in the keyboard. To be able to properly answer email, do presentations, write papers and so on, you need a laptop. the iPad can be a replacement with a dock and a keyboard, but it has less such functionality. In case you need an entertainment device, go for the iPad, which is wonderful for reading books and so on. I personally own a Macbook Pro and a small mobile with Android.

My choice would be a bigger Android phone (e.g. Desire HD) and the Macbook Air. Ipad 2 could make you wait for a while and may not be worth it. We don't know the specs, we won't know anything till the last minute. + there would be limitations such as the well known Flash issue. You want a "full web" experience that you won't have with an ipad.

I suggest Big Android Phone and Macbook Air. iPad is great for content consumption but not a good productivity tool.  When you are on the go, Android Phone is more portable and easy to use. When you sit down somewhere, Macbook Air could give you faster typing speed and more computing power.