I take my snakes out for photo shoots and usually put them in branches, or somewhere somewhat containable. I let larger corns play on the grass sometimes, but never a hatchling.
These play sessions are usually pretty short, and as soon as the snake gets fixated on burrowing (which is usually pretty quickly) then the play session is over. I have a lot more success with low branches. I feel more comfortable that I can reach the snake at all times, and they tend to have nicer poses if you're into having a photo shoot with them.
The idea of exercise is definitely good though! Depending on what kind of home your snake lives in.. tub vs tank, I don't think they always get the amount of exercise that is the most beneficial for them. Good luck, have fun and be safe!