Wow! Menu looks great. I assume you're not having ALL of that -- or are you?
I think your estimate seems reasonable, given the open bar. Lots of people would rather have a gin and tonic or whatever with their meal. But better too much than too little, especially if you can return some.
Lots of good discount wine places in and near the OC -- you can get some great stuff at any of them and probably pay less than from Navarro, and you could more easily taste it first. Check these:
High-Time Wine Cellars
Southern Hemisphere Wine Center
The Wine Club