Welcome to APUG. With the trip coming up so quickly I'd just go with what you already have. Maybe add a tripod - so you can catch slow shutter speeds and water (while keeping trees and rocks sharp). A couple filters for b&w may be useful, if only one; yellow or orange (Helps clouds show better against sky), then if you get another; green or red (options for occasional dramatic foliage or dramatic skies - don't overdo it).
If you want you could treat Yosemite as a New York "street scene" and shoot people (no filters needed). You'll find tourists from everywhere on Earth, backpackers (thru-hikers on the John Muir Trail - ask them what their "trail name" is) and other photographers hard at work.