NEO Scavenger has no official ESRB/PEGI rating, so the best way for parents to decide is to try the free demo for themselves. This way, they'll get a feel for the style of game and it's content.

If I were choosing for my own children, I'd probably recommend the game be limited to kids 11 and up. While there's no graphic violence nor sexual content depicted, there is quite a lot of descriptive, violent text. Bandits bash heads with metal saucepans, wounds get infected and pus-filled, and killing can be common in some games. The world of NEO Scavenger is a dark place, and there are mature themes such as slavery, cannibalism, and corruption. And items such as whiskey, prescription drugs, and medicinal plants are featured.

Ultimately, the demo is the best way to measure appropriateness. It's there precisely so new customers can decide if NEO Scavenger is right for them!