A treasure hunt is a great way to entertain a group of people, particularly at a children's party. There is a competitive aspect to a treasure hunt, but because hunters often have to work as a team it doesn't matter if the abilities of the hunters vary.
Treasure hunt clues (especially varied clues) are interesting little puzzles to solve, regardless of their difficulty. They give a sense of achievement to anyone who soles them. Having a mixture of physical challenges and mental puzzles makes it more likely for everyone to get involves. A scavenger hunt can get everyone warmed up, and can have within it something to give your brain a work out, for example having to make up a poem.
Theming a treasure hunt can inspire the imagination: pirates, princesses & knights, spies, animals etc are a great way to tie parts of a treasure hunt together and if you ask hunters to dress up it allows them to be creative too.
Of course, one of the most fun parts of a treasure hunt is the prize at the end. Always make sure the prize can be reached, and can be shared by all!