Here are some comments:
UNIVERSAL STUDIOS
I have never been, but I guess it's the thing to do if you're in LA and I'm sure you will enjoy it.
GRAND CANYON
It is magnificent and you don't need to take a helicopter trip to appreciate it. However, it's probably something you will do only once in your life so go for the helicopter trip. Because the canyon is so big and certainly if your time is limited, it will probably be the best way of seeing the magnificent sights.
One thing which surprised me about the Grand Canyon is that it rains there (at least it did on the south rim when my wife and I went there). I had imagined that it was all desert and dry. This was a July a few years ago.
ALCATRAZ
A must. Get headphones and do the tour. There were some bad guys in there but you will be moved.
MEALS
You can eat quite cheaply but allow for tips for everything (and Sales Tax if it's applicable where you will be).