A bucket, a spade, and a gold pan, fun for all ages.
Teach them to use a Swedish fire steel to start a fire. Bonus points if they get to break sticks doing it.
Glow sticks, painters tape, and a phone with dance music. My kids loved taping the joined up glow sticks to their arms and legs and dancing in the dark. Looked like glowing skeleton at a rave. Lol.
Catching frogs, always fun.
Fishing, also a good time.
Smores.
Frisbee/ flying ring, also fun.
Card games or other games for chill times or bad weather inside.
Tablet, blue tooth, and a few downloaded movies as a backup.
Ask them what they want to do. Then ask them to tell you what that looks like. Most speak in words but think in pictures and that can help provide clarity on their expectations and then let you help reset them if necessary.