Whenever I wind up in a situation like this, the first thing I think about is whether or not there are any children's stories, songs, or games that connect to the idea of a computer.
For example, I might look for a story about a messenger that my kids would know to see if it would help me explain the computer as a kind of personal messenger bringing you the information you want.
I also think of games where one player is in charge and tells the other players to stop or go. A computer makes all kinds of yes/no, stop/go decisions to figure out what information to display based on a user's input.
Are there local stories, songs, and games that might help here?
I also think of ways to help kids perform or act the parts of a computer. For example, one child could be a user, another could be a keyboard, another could be the processor, and another could be the screen. The user could ask the keyboard for something (by pretending to type); the keyboard could pass the request to the processor; the processor could tell the screen what to tell or show the user.
Generally, I think of a computer as a machine that can make your thinking visible or audible and that can share people's thinking across ling distances with the internet.
I hope some of this is helpful!