Gaborone City Nature Challenge 2020

can game species at places like Mokolodi Nature Reserve be included?

You need a FAQ anticipating these questions. I can post one if you like ...

Yes, game species in a nature reserve can be posted as WILD, provided they have bred, and that they are living off the veld and are not being supplementarily fed (other than a game lick or two).
If this is just a glorified zoo (or in fact any other zoo in the Gaborone area), it can still validly be observed for the challenge, but must be ticked CAPTIVE (or planted if a plant planted in the botanical gardens, or in city parks).

Captive/Planted still count to the City Nature Challenge. To some extent it is cheating, but all cities will be doing this, so dont feel bad. Especially important are street and garden plants which contribute to the fabric of the city ecology and support pollinators, insects, entire communities. Although planted they ARE the urban ecology and need to be documented. So although iNaturalist focusses on wild plants and animals, the City Nature Challenge also has a very strong component of urban ecology and documenting which trees and shrubs dominate different parts of the city in 2020 is a very important aspect of the challenge. Especially if Polyphagous Shothole Borer and other future factors (fungi, climate change, fashions, invasive status) are going to change the face of our future cities, it is very worthwhile to record it in detail, if you have the volunteers and workforce.
((see https://www.inaturalist.org/projects/polyphagous-shothole-borer-beetle-pshb-atlas-s-afr & School Gardens project - still being designed )).