The activities I can suggest you doing in two days at Yosemite are: 1. Top of Yosemite Falls Trail 2. Vernal Fall and Nevada Fall Trails 3. Lower Yosemite Fall Trail 4. Tuolumne Grove Trail 5. Glacier Point
I know what you are thinking, Yosemite National Park is huge, what can you possibly see in two days? I think you can still see a lot if you know how to manage your time.