For me, when you go on a safari is really not the time to a) learn a brand new type of camera, b) learn all about wildlife photography technique and field craft, and c) gain supertelephoto photography skillz.
That's a lot of knowledge to gain that most of us get only from years of experience. Wildlife photography, like sports photography, is one of the harder genres to master and requires more specialized equipment than a simple entry-level dSLR/mirrorless kit.
Firstly, I'd also say as someone who shoots birds in flight and owns full-frame and crop dSLR gear and 2x crop mirrorless gear, that you don't want mirrorless for this, unless you plan on shooting a lot of animals that don't move. While for most uses mirrorless is more than equivalent to dSLR in image quality, the tracking AF performance--and more importantly--the supertelephoto glass with fast AF performance simply isn't there yet in the way it is on the dSLR side of the fence. There are really only two bodies that can do tracking AF (Oly EM-1, Fuji XT-1), and those will be top-of-the-line bodies.
Secondly, you'll really really want at least 300mm on APS-C, if not 400mm, 500mm, or 600mm. And these lenses are astronomically more expensive than a simple 70-300 el cheapo telephoto zoom. They tend to start in the US$1000 range and go upwards from there. The more speed you want, the bigger and heavier those lenses are gonna be. And handling them, physically, becomes more of a task than most newbs suppose (see: Roger Cicala of lensrentals demoing how one supports supertele lenses on youtube; as well as his videos on Nikon and Canon superteles.) Those are the type of lenses that National Geographic wildlife photographers use. Disabuse yourself of the notion that just getting a system camera will net you those photos. With a 70-300 zoom lens, you're not going to have the AF speed or the max. aperture, or the reach to get those kinds of shots.
Doesn't mean a 70-300 won't work for you, but it could be that simply using a bridge camera might work as well for you, depending on how picky you are about image quality and what other things you plan to shoot. If your reflexes are good, and you can time a shot, however, a bridge camera won't make you as happy as a dSLR, since the shutter lag time is going to be a bear.
You may also, if you weren't planning on using this setup at home regularly for birding or backyard wildlife, also consider simply renting the gear for the trip, and trying to figure out how much time beforehand you're going to need to learn to use it all effectively.
I would say, learn telephoto lens technique. Keep your shutter speed above 1/focal_length (or 1/focal_lengthxcrop factor, so for a 300mm lens, on a 1.5x crop body, then you want your shutter speed to be 1/450s or faster) to avoid camera shake blur from handholding. Learn how to hold a telephoto lens (actually, make sure you know how to hold the camera) or make sure you have proper stabilization. Learn to shoot short controlled well-timed bursts. And master back-button autofocus with tracking AF.
But above all, with wildlife--patience and timing are everything. Knowing your subject and its habits is everything. Field craft is everything. The longest lens in the world won't help you if you make a lot of noise, alarm the subject with body language or are simply unaware that the wildlife is there.
Practice at a local zoo. You'll see what I mean. Most folks will walk up to an enclosure, talking all the while, expect the animal to pose/perform/do something in the five to ten seconds they deign to give it attention, and then walk away. Whereas if you're willing to just sit in front of any enclosure for half an hour and observe--you'll see something worthy of taking a shot.
