Lived there for a few years, though prior to the recent change in concessionaire, so not as confident answering food questions. Some random thoughts:
If you're coming from the Bay Area, you'll probably come in on 120. I'd stop at the Tuolumne Grove of Giant Sequoias on your way into or out of the valley, at the junction of 120/Tioga Rd and the Big Oak Flat Road that goes down to the valley. You turn onto Tioga Road, drive half a mile or so, and park. It's only a 1 mile hike downhill to the giant sequoias, which are still impressive even if you've been to Muir Woods before. Even if they're not, you only wasted an hour or so!
This time of year, I'd recommend a destination hike and a valley day. You might need to be flexible which is which, based on the weather.
For the destination hike, one option is one-way shuttle to Glacier Point (which will stop at Tunnel View on the way up). Then, hike down the Panorama/John Muir/Mist trails back to the Valley... Or go up those trails and get a shuttle back down to the valley if you're confident in your ability/timing. That's most of one day, with some time left over for sitting by the waterfalls along the way and the river when you're finished, reflecting.
Or, head up to the high country on the way in or out from the bay area, and hike either North Dome or Clouds Rest (details below). Drive exhaustedly but safely to your tent cabin or hotel, depending on which day you do it.
Things in the Valley:
Stop at Bridal Veil Falls on your way in as you likely won't get there again.
A bike ride around the valley is spectacular, and you can rent bikes. Bike trails go roughly to the Yosemite Lodge/Camp 4 area, but you can go further west down to El Cap meadow, which is worth it. The shuttles are easy and frequent, too, though sometimes crowded. Avoid driving, even though it's getting late in the season. There will be traffic and parking issues. There's a shuttle to the west end of the valley (El Cap meadow/ Cathedral meadow area) that is likely still running its 'summer' hours. I'd take that down and walk back along the river to at least Yosemite Lodge where you can pick up the more regular shuttle back to Curry/Half Dome Village.
You could stroll from Curry/Half Dome Village roughly straight across the valley to the Ahwahnee/"Majestic Yosemite" Hotel, have the fancy brunch or a coffee, and then walk east to Mirror lake/meadow, which is right beneath Half Dome and a nice viewpoint.
On your way out of the valley, stop in El Capitan meadow, walk up through the woods to the base of the wall, and look up. Walk back across the street, and sit in El Cap meadow and look for climbers (ideally with binoculars), appreciate the place, and be sad that you are leaving ;-).
Generally:
(Upper) Yosemite Falls trail is not too exciting in the summer/fall, as the falls are almost, if not completely, dry, and the trail itself is exposed, hot and dusty.
As others have pointed out, the bears are for real, don't leave anything in your car. And please don't stop in the middle of the road if you see one. Lots of deer, too, that seem almost tame but certainly aren't, especially as the bucks start to get interested in fighting over the does this time of year. Have seen some good deer-jousting in the school playground (near valley loop trail between Lower Yose Falls and the Ahwahnee).
For my money, hiking up Half Dome is vastly overrated. Unless you're a true peakbagger and have to check it off, it's actually rather strange to be on top and.. umm, not see Half Dome from wherever you are. Also not the most enjoyable dayhike (other than the Vernal/Nevada Falls sections). Lots of elevation, lots of people, scary slab, hassle with permits. Nice views, though.
Hike info:
Clouds Rest from the Tioga Road (~1.5 hour drive from Yose Valley) is spectacular, and also about 15 miles r/t, and a lot flatter than Half Dome (though not flat! maybe 2000' climb vs 4800' for HD). You end up right across from Half Dome, but 1000' higher, and it's really wonderful. Stellar view down into Tenaya Canyon, can see Tenaya Lake, and great views of the high country. Hardest part is right at the beginning.
North Dome from Tioga Road is similarly flat with a lot less elevation gain than Half Dome, shorter drive (1:15) from the Valley, and shorter hike (~9 miles r/t) and you also end up almost across from Half Dome and overlooking the valley. If you were to do either of these day two, you'd likely head right home afterwards, so make sure you've had time to sit in the meadow next to the river and just stare upwards already!