If you are going to teach it with the child who is 7 year old, you are going to use the word that can easily understand or comprehend them, but it really depends on the child if the child is not interested they will not easily understand it coz we all know that age is not the age that a child will give time to understand it. There is a child who are very curious but only few.
Precisely, I guess it will be tough for you teach a 7 year old because as far as I know they all want is fun and they don't care about earning future. Though they are curious in many things still they prefer to waste their time on playing rather than earning. Maybe you should teach them if they are on the right age.