Peoples Square and the Shanghai Museum (which is actually in Peoples Square) are really easy. If you want to go to any specific restaurants, having their phone numbers handy will be good. Pretty much all taxi drivers have cell phones these days, but you should also carry your own (save your hotel's phone number as well; the concierge will be useful if you find yourself in a pinch).

Your wife will not like Line 2, and I am unable to qualify this statement with "during rush hour" because it is always packed to the gills.

Go for the Andaz or HOTB if you care more about location than room quality. I lived in Lujiazui 11 years ago (very nice apartment), but I regretted the decision because crossing the river in the evenings was extremely annoying no matter how I played it.