Phil,
Having worked at Yosemite I can say that if you are into hiking, photography, nature viewing, or just site seeing, two weeks there will go fast. 80% of the park visitors only see 20% of it. Most of Yosemite is wilderness area but most visitors only go to the Valley Floor and Glacier Point, some drive through Tuolumne Meadows. There is a good shuttle service in the Valley.
A good hike, not to strenuous, is take the shuttle from the Valley to Glacier Point and hike down the Panorama and Illilouette trails, great view of Half Dome, Illilouette Falls and Panorama Point then on to Nevada Falls and the entrance to Little Yosemite Valley, from there you can take the "stairs" down to Verneral Falls and then on into the Valley. This is a great one way hike and one of many in the Valley.
Tuolumne Meadows has some great day hikes along with its backpacking. Hikes like the Glen Aulin trail to Tuolumne Falls is a doable day trip, if you are in some shape and acclimatised to the altitude.
Check out the visitors center in the Valley, great movie on Yosemite, and loads of information. The Ansel Adams studios has a free guided photo hike around the Valley, you have to sign up early.
Check out
http://www.yosemitehikes.com for lots of information.