Sounds like the OP has a really solid foundation to get into this with experience in other water sports and swiftwater training. I think with a positive attitude and perseverance, you're going to crush it! California is tough for mellow rivers - maybe heading up and boating the Sacramento River could be a good family trip. Here's a video of some guy running Redding all the way to the delta. The Sacramento - At Current Speed | Cataract Oars. The American downstream of Folsom is also really chill for the family. As others stated you should definitely get out on some commercial trips to see how the family enjoys that.