Wow, lots of good tips!
Remember that this is the park that Walt built. Obviously there are many changes since he died in the 60s, but the layout and the feel of the park is consistent with what he originally intended. You'll find rides at DL that you won't find elsewhere and some rides, which in my opinion, are better than those at WDW.
Let me get a little off the beaten track...
1) Take the Arts Tour at the Grand Californian. We're assuming that you're using DVC points to stay at the VGC. If you are, you'll find the lobby of the GCH to be really impressive. The tour, which is free, shows you a lot of hidden architectural and decorative features of the hotel, which interested me. I've taken the tour twice. It was a little different each time.
2) Going with the assumption that you're staying at the VGC, make use of the back entrance from the GCH to DCA. Only guests of the Disney hotels can use this entrance into DCA. It also opens before the main gate opens, which is an advantage to get Fast Passes for the World of Color. You can also get on some of the rides before the masses arrive.
3) A PP mentioned to notice the small things. This in my opinion is what differentiates a Disney park from a generic amusement park. For instance:
a) Notice the candle in the window above the fire station. That was Walt's private apartment and the candle is there to remember him.
b) Notice the sounds coming from the windows above Main Street. Like WDW the windows are also dedications to people who have contributed to the park and the company.
c) See if you can find duckzilla in the Storybook Land. Ducks like to waddle around among the miniatures so they are by comparison huge. Storybook Land at night is a completely different experience than in the day.
d) Look up. Virtually everywhere there are interesting things to see if you look up.
You also mentioned that you might try to see other things in the area. Having grown up in California, I suspect that the redwoods are too far for a day trip. But you could consider driving up to Solvang, north of LA. This is a Danish community with Danish restaurants and shops. You'd have to look at Google Maps, but Hearst Castle might be a day trip. Going south you could go to
Legoland which is fun. San Diego is about two hours south of the DLR. They have an aircraft carrier that is a museum, which is very interesting. There's always the beach too.
Hope you have a great time!