This sounds risky, confrontational, even dangerous. Consider setting up different levels of perimeter security. Think more about first giving intruders an easy way to back out and just leave (vs. "letting them get right into the garden and then a crazy fucking loud alarm goes off"), rather than perhaps forcing panic and engagement, which you don't want if they are low-life or professional criminals, junkies, gang members, have more and better weapons then you, etc. For example, rather than all that noise, why not simply first have a load of lights come on, and then if they get closer all hell breaks loose. Also, staged responses should reduce inner security false alarms by scarring off more animals. Maybe consider installing a remote loud PA or speaker system or radio so you can threaten intruders?
But the big question is: What are you and your guards going to do, if all the noise doesn't scare them off?
If you are legal, why not just do like most every local business and many residences do? Why have guards? Use your burglar alarm to call in a police response, maybe even have a professional service monitor your system (shouldn't cost more than $1/day), or hook in a cell phone that calls you and the police. Don't you want local police to respond immediately if a real burglary, maybe home invasion, is taking place?
