Tripod and lens hoods. Two things that will greatly improve the negative quality from your 35mm.
For B&W -- a yellow filter, perhaps a red. They'll see more use than the polarizer, which is still nice to have. Using the filters, slow film (for finer grain), getting some DoF (depth of field) and taking photos in low light all call for a tripod.
And you might consider a longer lens or two -- those Falls and peaks are a long way away!
PS -- Yosemite Valley will be a crowded zoo, but you can still escape the crowds by getting up early. I do most of my visits in the winter, but you will have access to more of the Park. Up around Tenaya Lake, parking in a pull-out and wandering about can be nice (and private). The least crowded days in the summer are Tuesdays and Wednesdays (according to the shuttle bus driver I talked to -- he should know!)