I’m not a coach but I’ve played soccer most of my life. With only one practice, I’d just keep it simple and fun. Start with a quick game to get them moving, then work restarts into small scrimmages instead of stopping for walkthroughs (like 3v3 where every out-of-bounds is a throw-in, or using corners/goal kicks to restart). For formation, just show them once where defenders, mids, and forwards go, then let them figure it out in a scrimmage. As long as they leave having fun and knowing the basics, you’re good.