My nephew wanted a laboratorry set. His grandparents complied. Then he started raiding the kitchen for materials and requesting slow-burning fuses - he was intending to make explosives!
So, I bought him a book on pumpkin chunking and other delightful ways to make object fly while making big booms. Since the only location in our backyard that a trebuchet would be able to work resulted in two houses being spattered with pumpkin entrails, nephew and his best friend made the war engine at the friend’s house.
Only their flock of sheep was terrorized.
/johnny