You can control the invitation list for each event in Scoutbook, and only people that are invited to a particular event will get the email reminders. The events will still show up on the calendar for anyone that visits it directly, or is subscribed to the calendar.
What you can do, as a work-around, is create a “phantom patrol”, since each patrol gets their own calendar, and add the events you don’t want to be on the website to that calendar. We do this for our school district calendar, since we need to see those dates when planning, but not during routine Troop operations. It’s not perfect, but it works. You can’t invite anyone to the “phantom patrol” events, and they’re still visible from the Scoutbook calendar. They’re just not part of the top-level Troop calendar, so if you sync to that, they don’t get carried over.