I absolutely do not think you should feel guilt about this. While I don't at all consider playing on a playset in grass risky (at all), it might be helpful to learn about the benefits of risky play, bumps, bruises, and scrapes. Kids are actually safer if we let them learn their own limits and this involves some risk. The general world at large is hard on parents these days - you can't win, and I understand how the guilt creeps in - but we need to let kids explore and not try to prevent all potential scrapes.
Not the greatest source but I can't find teh article I like on risky play - this goes over some of the benefits,
https://www.scarymommy.com/let-kids-take-risks-playing-outdoors/