As you get closer to my age (70) here's a few more alternatives:

1. Rebounder (NO to LOW impact). Jumping jacks are an especially good cardio on the rebounder, particularly for aging knees:>))

2. Kettlebells (NO impact! and combines cardio and strength

3. Resistance bands (much gentler on the aging body than dumbbells - at least, in my experience)

4. LOTS of simple dynamic stretching. Here's a routine I put together a year or so ago that I still do on most days: https://www.youtube.com/watch?v=xLlE7csP1KI