Yosemite:
Kind of depends on how much walking you want to do. Without doing much walking you can visit Bridalveil Fall on the way into the park. And you definitely should go to the Tunnel View area - you'll drive right by it if you come in on Highway 41, otherwise you can either make a short side trip (about 5 minutes up the road) to go there on your way in, or stop on your way out. The view is better in the afternoon than the morning because of the direction of the sun. Then park your car in the Valley (either in the day-use lot, or at wherever you are staying) and take the (free) Valley shuttle around the park. Go to the Visitor Center and Lower Yosemite Falls - there's about a 1/3 mile loop trail that will take you to the bottom of the falls.
The shuttle will also take you to stops for LeConte Memorial, Curry Village, Happy Isles, Mirror Lake, and the Ahwahnee Hotel. Depending on your time you may or may not want to get out and see the Memorial and the Ahwahnee. Mirror Lake is a fairly long walk, and the best time to do that is early morning when the shuttle isn't running anyway.
But if you don't mind about a 3/4 mile walk (one way) with about a 500' elevation gain, I would highly recommend the hike from Happy Isles to the Vernal Fall Bridge - along that trail you will get a view of Yosemite Falls looking back up the Valley, and a view of Illilouette Fall, which is only visible from that particular trail. And of course you'll get a great view of Vernal Fall from the bridge. The Nature Center at Happy Isles is kind of interesting, especially if you have kids.
If you want a guided tour, I've heard good things about the Valley Floor Tour, which takes you around on an open tram. They will tell you about the history of the park and some of the geology, too. And they will take you to the tunnel view and some of the other places I mentioned - no hiking on this one, though.
If you want to do your own Valley Floor tour, just take the one-way road all around the Valley - I think it's a 9-mile loop. After you leave Yosemite Village you'll pass by Lower Yosemite Fall (but there's not much parking there, so I recommend you visit this from the shuttle instead) and after a couple of miles you'll be right in front of El Capitan. Pull off the road and bring binoculars to see if you can find any climbers on that huge rock. Once you're back on the road you'll go about 2 more miles and the river will be on your left - there are several parking lots there where you can pull over and go look at it - though how impressive it is depends on when you're there - it's quite impressive during spring run-off, not so much in July and on. You'll have to turn left to continue on the one way road - just after you cross the bridge there's a pullout on the right for Fern Spring - this is a pleasant little area to stop and see. Not much to it, though. As you continue around you'll pass by the Bridalveil area, where you can stop and walk to the base of the fall - it can be pretty wet depending on how much water is coming over and how the wind is blowing. But you can see it from a distance without getting wet. There's actually a very nice view of it from the parking lot, or, if you continue on the Valley floor road you can see it from there too. Be careful in that area because there are lots of people pulling on/off the road. Another mile or so up the road there's a meadow on your left and you can look across and see both upper and lower Yosemite Fall. There are pullouts along the road - but again, this is one of those areas with lots of traffic. And that pretty much brings you back to the Village area again.
I highly recommend the drive to Glacier Point, also - that's about a one hour drive from the Valley, and you get great views of the Valley, Half Dome, and the mountains in the Sierra from there. You *could* do that the day you leave to go to Sequoia, though it will cut into your Sequoia time.
Wildlife sighting is just luck, except for squirrels - you'll probably see lots of them at the tunnel view area, and elsewhere in the park where people are eating - they are pests looking for handouts.
If you're out near any of the meadows early in the morning or in the evening you will probably see deer. (They are especially common in the meadows near Curry Village.) I've only seen raccoons at the pizza deck at Curry Village. There are no wolves and bear sightings are just one of those "right place at the right time" things.
Normally I would recommend stopping at the Mariposa Grove of sequoias on your way out of the park, but since your next stop is going to be Sequoia/King's Canyon, which has bigger trees, I think you can skip that. Though that's the place that has the tree you can walk through - I don't remember if there's one of those in Sequoia/King's Canyon or not.
Sequoia/King's Canyon
Based on your wording I'm assuming that you're going to Sequoia/King's Canyon from Yosemite, but if you're going there first, and entering Sequoia National Park first rather than King's Canyon, then just reverse the stops.
If you're coming from Yosemite then you will first enter King's Canyon National Park, and then take the Generals Highway into Sequoia National Park. I would recommend stopping at the Grant Grove in King's Canyon to see the huge trees there. And stop at the Visitor's Center. Then depending on how much time you have, you can head straight for the Sherman Grove and walk around that. And then stop at the Auto Log (this is the fallen tree that you can drive across - or you could last time I was there). And if you have time/energy you can climb up Moro Rock - it's short but steep. Nice view, though. Not much else to see as you head out of the park from there, though I'll warn you that the road is twisty and slow-going as you go down towards the park exit. There's another visitor center near the exit, which may or may not be worth a stop depending on time (they have restrooms, though).
Hope that helps - let me know if you have more specific questions.
