First of all if you tell an employee we pull out at 7:30 he better be there. We don't wait for them. If they can't make it on time then they are not someone I would want to keep.
As for the equipment bonus. A lot of responsibility falls on you as the owner to keep up with everyday wear and tear. Mistakes happen and you can't fault them for a belt breaking or nail in a tire.
Why not just say that you give a Christmas bonus of a certain amount. Maybe $100 per month. This bonus is based on how well and hard they work or production. You would then dock the bonus for problems that come up..... If "ms smith" calls all the time to complain about the edging or weeds in beds take some off.