chelmkamp

I can't speak for the UAE portion of your trip, but as for Nizwa and the surrounds, you may want to consider adding the Jebel Shams, a wonderful Grand Canyon-esque panorama relatively near Nizwa and Bahla. You need 4WD to drive to the top yourself, but (and I haven't seen this in a guidebook anywhere, just happened to discover) there are 4WDs and drivers conveniently hanging out at the end of the paved road on the way up the Jebel. Bargain hard, and they'll happily drive you to several vistas at the top. Most don't speak English other than money, so don't expect any good narration unless you speak Arabic.

Bahla fort, about 40k from Nizwa, is also interesting (two UNESCO World heritage sites in the surrounding area -- the fort, and the ancient irrigation system). Perhaps more interesting though is wandering the mud ruins below the fort (you can't enter fort itself as it is chronically under refurbishment) where some poorer families still live in the crumbling remains of an awesome former city. If you look carefully, you will see where vast arcades of the old city were later converted into small homes, and with an eye for architecture you will notice all kinds of interesting mud building methods in the rubble.

Sorry for the wordy reply but these two sites (Jebel Shams and Bahla) are some of my favorite places in the entire Gulf, and I think any visit to the Nizwa area without them would be a loss. (Nizwa fort is cool and one of the few you can see inside, but it can get crowded with tour bus crowds.)