I haven't seen these for trawlers, specifically. But, the ASA offers a ton of standardized courses for sailing, and the majority of the knowledge is transferrable. Years ago I took the 101, 103, and 104 courses: basic keelboat, coastal cruising, and bareboat charter, and they provided a solid baseline that applies to any kind of boating. The majority of the courses have to do with boat systems, maintenance, troubleshooting, safety, navigation, disaster recovery, docking, and anchoring. We spent about 20 minutes total on sail trim.
Also, the ASA courses are family-friendly and usually pretty affordable. They’re designed to be casual weekend affairs. I think the Coast Guard offers more intensive courses, but they are set up more like a college class.