Definitely need more info regarding what you're looking to do and where you'll be staying. You won't need two days in SM/Venice. They are essentially right next to each other and there isn't enough to do at each that you'll need two days unless you just want to spend a bunch of time lounging on the beach while looking at water you probably won't want to spend too much time in (it's fucking cold). The bike suggestions are good. You can rent them on the beach and ride between SM and Venice to see the sights. SM has a ton of shopping your wife might appreciate and some good food (I think Father's Office opened a location in SM and they have a fucking legit burger).
The Getty is a great suggestion as is the tar pits. The par pits are actually right near LACMA, so you could do both of those in the same day. But keep in mind that area is a clusterfuck for parking and traffic so make sure no one is hungry or needs to pee cause you might end up killing each other while trying to get to LACMA if you get in bitchy moods. Breathing Light is a pretty awesome experience for the art fans: https://www.lacma.org/art/exhibition/james-turrell-breathing-light.
Someone above mentioned Din Tai Fung. It's a must if you like Xiao Long Bao (soup dumplings). They are far superior to anything you can find in Texas. I also suggest Sugarfish and KazuNori if you like sushi/handrolls. Howlin' Ray's has an insanely good Nashville hot chicken sandwhich, but the wait can be awhile. Fortunately, it's in Chinatown, so part of your group can walk around a bit while the other part waits in line.