I had similar questions and emailed the Times Square Alliance and the Department of Transportation, and actually got quick answers :) Most of the theaters aren't actually on Broadway, in fact there's only one: The Broadway Theater between 52nd and 53rd streets, and the closure does not affect that theater. The Times Square Alliance thinks it best that people using wheelchairs and the like are dropped off in front of the theater, the DOT thinks 7th Avenue is best. (I'm not sure what dropping someone off on 7th Avenue will be like now, as they have lengthened the green lights by 20 seconds... does that mean the red lights have been reduced a corresponding amount?)
If you do pass through the new pedestrian plaza, there are currently lawn chairs set up so your wife can take a break. I'm not sure if they'll be a permanent fixture.
As for parking, check out http://nyc.bestparking.com/
. Have a great visit! What show are you going to see?