I think that there is a huge age range that might be acceptable.
Some kids shouldn't ever be allowed around anything with a gas engine.
Some kids take to stuff like this right away.
Some kids beg.
Some kids would have a complete fit if asked to help out.
You really can't pass a blanket judgement call on something like this.
I am a farly protective parent.
My son is 9.
He LOVES LOVES LOVES to mow. It is like a 'thing' for him!
He has been pushing toy mowers, and an old-fashioned reel mower, since he could walk. He has been riding on DH's and Grandpa's lawn tractors since then too. He is very capable, and we let him mow sections of our lawn at a time, with just some oversight and guidance. Not a lot of actual supervision.
We would have a hard time trying to tell him "No, you can't help mow the grass". He would beg. He loves it and he feels mature and like he is helping out!
