Your list looks fine but i advise you do the following:
Have a look at these links, i hope they will be able to give you a clear picture:
http://www.immigrationboards.com/viewtopic.php?t=91068
http://www.immigrationboards.com/viewtopic.php?t=91024
Yes, take photocopies, it may save you time while there.
Take the photos if it gives you a piece of mind
Take all documents with your names & address on ( that way you submit what they ask for)
You don't need her mother's passport copy.
Make sure you are using the current SET M form. Don't forget the photos too!
Good luck.