That Was Then In the early 80s, my family set off on an annual trip from southern Ohio to Wisconsin’s North Woods. My youngest nephews, toddler twins, spent 750 miles in a playpen in the back of their dad’s minivan, holding on for dear life and joyfully yelling “whoa” on the biggest curves. Child restraint laws didn’t go into effect until a few years later. We didn’t know what we didn’t know. Recommendations concerning safe sleep, mealtimes, limit-setting—and, of course, car seats!—have all changed in the decades since today’s parents were kids themselves. If you’re one of the millions of U.S...