More info required on the project scope, such as :
topography of the lawn
dimensions of the lawn
shape of the lawn
obstructions to clear line of sight for all transmitters/sensors
height of "walls, roof and tree"
Alternative(1), hire "staff" to do the cutting - they come in various "versions", are expensive to run but can be used for other tasks and you can get a new model every year.
Alternative (2), exercise your butt.