Hi Mrs. B-
My LO isn't too keen on sitting on the grass (I think it feels pretty strange to her) so I keep her on a blanket outside. Generally, I also find that before she actually tries to eat something, she picks it up and stares at it before "tasting" it so I have plenty of time to intervene. Plus, the texture of most stuff outside is kind of unfamiliar, so in the case of my LO and the leaf she tried to eat last fall, she just choked on it before ingesting it. Also, provided your lawn/outside area isn't sprayed with fertilizer or pesticide, I wouldn't worry too much about it anyway.
Have fun!