We used to have a contract similar in scope, it was a boat yard for dry docked boats.
This job will take you significantly longer than you think it will I suspect. The job we did was a little smaller than yours, I sprayed out of the back of a pick up truck with a 50 gallon sprayer. We sprayed 2x per year, soil sterilant was not allowed due to large trees surrounding the property.
It took me almost 8 hours to spray each time, walking between all the boats, moving the truck takes a long time.
I thought you had a decent price until you said it included mowing, I would not touch that job for $700 per visit (based on the numbers you gave $2000/3)
I dont know what your market will bear or your costs but, I got over $2000 per visit and still hated every minute of it.