Tips for helping my mom to get in shape!

So, my mom has lost quite a bit of weight thanks to a dieting program and walking, and now she wants to tone her body and of course, keep exercising for her own good. The thing is though, she doesn't want to go to the gym or join a group or something like that since she doesn't yet feel confident enough, and also she has quite complicated worktimes since she works both away and at home.

I am really into fitness and would love to help my mom with workouts at home, but I have no idea where to start since I'm not a beginner myself! What kind of exercises, how to build the workout etc .. What's the best way to get started? She's almost 50 years old and has trouble with her knees just like me. Nothing to major though.

Anyone around her age who has just gotten started and would like to share what kind of exercises you're doing? Or anyone else who has something to suggest? I'd love to hear what you think!