Kids to camp at 2:00, wheels toward the trail by 3:15. Every time below is re-cut for a fast pace so you bank the hatchery view and the full Fire Tower loop with real daylight to spare.
Follow the park's yellow & brown arrows from the Nature Center trailhead. They run the loop counter-clockwise, which front-loads the sustained climb so you top out at the CCC tower near the midpoint (~1.5 mi in) while your legs are fresh β then the back half is a rolling descent home.
If a posted arrow ever disagrees with this, trust the arrow β they're maintained on the ground. Stay on the arrowed loop; unmarked connectors branch off mid-trail and are the easy way to add accidental miles.
Missouri state parks are free β no day-use pass. Grab a paper trail map at the Nature Center if it's still open when you arrive; the loud pyrotechnic vulture deterrent near Campground 3 only runs ~8β10 AM, so it won't affect your afternoon.