Hello, Alsan.
That's a pretty small plot, you certainly do not need verifocal cameras for a 6x3m plot. You may want to consider going IP so you can get a nice mid-range camera like https://www.securitycameraking.com/product/4mp-e-series-2-8mm-starlight-ip-turret-dome-camera-w-audio/ which can give you a little bit of digital zoom to play with while still recording at a full 30fps. I'd pair that camera with the https://www.securitycameraking.com/product/elite-series-4k-8-channel-nvr-with-8-poe/ 8 Channell NVR to cover all your bases. 4TBs on 5 4MP cameras should get you at least a month of recording.
I'd need to know more about your back yard to make any specific recommendations, but the cameras I mentioned above are good overall cameras that can work in a variety of circumstances. If you are interested in ordering, please email me at afrassinelli@securitycameraking.com or feel free to contact us over the phone at (866) 573-8878, my direct extension is 137.
Thank You,
Aldino Frassinelli.