AppInventor is a free program from MIT for making Android apps. It's easy for beginners to use, but has powerful capabilities for creating fully functional complex apps. Newcomers to App Inventor can have their first app up and running in an hour or less, and can program more complex apps in significantly less time than with more traditional, text-based languages.
There are excellent tutorials on the AppInventor web site. Before mentoring at CoderDojoTC it would be great if you went through the start up procedure and followed some of the beginner's tutorials to make a few apps -- like Hello Purr, Paint Pot or Magic 8 ball. Other apps that are good for beginners are Mole Mash and PicCall. When you (or your students) are ready for something more challenging, try the tutorial for Mini Golf or Pizza Party.
After you create each app, think about ways you might like to change, enhance or customize the app, and try to do that. Or look over some of the instruction menus and explore new commands. Some of the tutorials have challenges or suggestions for enhancements at the end, an excellent way to re-enforce learning.
The laptops at CoderDojoTC will have AppInventor and the emulator loaded. There are also some Android phones for testing. Please familiarize yourself with the download process, because many kids bring their own computers and will need to download the software before beginning.
Thank you for mentoring at CoderDojoTC!