Recently there are enough wineries in Malibu that there are now companies that will take you from winery to winery. I've never done it but I know of two couples that did it. See https://www.tripadvisor.com/Attractions-g326… The advantage of the tour company is that they can make suggestions of where to go and they are the designated driver. The two couples that I knew also opted for a picnic lunch supplied to them between wineries.

The closest major wine area that I can think of is northwest of Santa Barbara, in the Santa Ynez Valley, not that close to Magic Mountain. Santa Barbara has some wine tasting rooms. It's faster to drive directly to Santa Barbara from Hermosa Beach, rather than going via Magic Mountain. Somewhat near Magic Mountain is Ojai. It's a cute western town. Unless you are horseback riding I don't think that it would occupy much time. We have driven from Manhattan Beach to Ventura to Ojai to the Magic Mountain area and back again on the freeway just for a scenic drive.

There are other things that you could do or see, but they are pretty sedate compared to wine tasting, and I would feel like wine tasting after multiple weeks with multiple kids. If the kids aren't returning until late at night you could all get an evening at the Hermosa Beach Comedy and Magic Club. On Sundays Jay Leno performs. I like Laguna Beach, both for the scenery as well as the art galleries. A day trip to Santa Barbara is also an idea. If you have specific interests you can get a lot of good suggestions.