I believe all C4 plants are in the grass family, including corn and sorghum. Switchgrass might also be a C4.
Don't choose to grow a plant based on the pathway it uses for photosynthesis. If you are a small landowner who is not interested in deriving income by harvesting plant materials from your land, plant it for your enjoyment.
Native woody plants will sequester C from the atmosphere. They'll be relatively care-free after establishment. Woody plants will be better at C sequestration than grasses and other herbaceous plants. That being said, if you need a place for the kids/dogs/what have you to run around on, you'll need some grass. You'll want some flowers. Maybe you want a veg/herb garden.
If you derive anything from the above babble, it should be:
-plant as much to woody vegetation as possible;
-go with natives, if possible.
-don't worry about THE most efficient CO2 absorber.
