The Dahua 5442 series cameras (including the camera you linked to which is a 5442 series camera being sold under a different name badge) are certainly not the cheapest cameras out there. But they offer the best combination of performance vs price. Spending $100 on a camera that doesn't work at night is not a good deal. If a camera isn't capable of providing high quality footage in low light situations (when it is most likely an "event" is going to occur), then it isn't worth buying. You would do well to consider something like the 5442 series.
That being said, the variable focal length cameras are more expensive than their fixed focal length brethren. Variable focal length cameras allow you to change the "zoom" of the camera and it allows you to really dial in the coverage area of the camera. A fixed focal length camera doesn't have any "zoom" and you simply see what the camera was set for initially.
While having at least one variable focal length camera can be helpful to find out what might work for your use case (by moving in around to each location you want a camera and then playing with the "zomm" to find out what focal length works best), you can also use online software to help with this.
Check out the
IPVM Calculator which allows you to overlay exact camera models over a satellite view of your exact address. I have found it very accurate. It allows you to compare the field of view of a 2.8mm camera to a 6mm focal length camera, et, etc, etc. I'd recommend overlaying the different models of 5442 cameras until you find one that works best. The variable focal length models will allow you to change the "zoom" on the software while the fixed focal length cameras will not. You may find that a 2.8mm or 3.4mm version of the 5442 series will work just fine for your situation and will allow you to save some money over the variable focal length model. There is no point in getting a variable focal length model if you are just going to set it to 2.8, or 3.6 or 6mm because those are all available as fixed focal length models which cost less.
Be sure to pay attention to the PPF number (pixels per face) on the right side of the screen. This number changes as you change the distance from the camera. The higher the number, the higher the resolution of the image and the better you will be able to identify someone. You really need something like 75 or greater if you want to be able to identify a stranger is good lighting conditions. But you really want that number as high as possible.
. 
