Introductory/Beginner books on Buddhism, but for children There are a few posts on the site asking for good introduction/beginner books on Buddhism, but I can't seem to find any that a child could read and understand.

Although age range doesn't really matter to the answer that people might post, let's say someone between the age of 7 and 14, just to have some context.
I don't have a title for you but there are the Jataka Tales which would introduce some Buddhist ideas to entertain and there are english publications of these.

However if the child is over 7 years old it is possible that they would understand whatever you throw at them in regards to the Dhamma, there are mentions of very young Arahants from the time of the Buddha.

Other than that there are the Gathas (poems of the Elders) which come to mind if you are looking for something like that.