What is the best way to coordinate these two activities? Capetown first or the safari? Best way to travel between Kreuger and Capetown?
There is no right or wrong way - it's more a question of what fits with your itinerary and what you can find the keenest price on. Also, whether you are going on a package (where transfers from airports to accommodation are covered), or organising the trip yourself.
Where are you flying from/in to? The reason that I ask is that it may be easier to get a direct fight to Cape Town, but more likely you'll have to bounce through Johannesburg. Often there's very little difference in the cost of incoming flights to both destinations, so if you have the chance, book yourself through to Cape Town on a single ticket (which also covers you should you be delayed on your incoming flight and miss your connection).
I personally believe in getting the longest leg of the journey over and done with first, so I'd fly to Cape Town, enjoy your time there and then connect to Kruger Park. The options for how to do this would be to fly to Johannesburg and then pick up a hire car or a shuttle organised by your tour operator - which should take 4-5 hours (depending on where your camp is), of which the first 2-3 hours are rather dull. An alternative is to fly directly from Cape Town to Nelspruit and pick up a hire car/transfer from there, which then only leaves you with a 1-2 hour drive at the most. SAA fly this route direct, which is much easier than the other flight-based alternative of flying from Cape Town to Jo'burg and changing plane.
Remember that South Africa drives on the left hand side of the road like the British, so you might want to take this into consideration if you are thinking of self drive. The road system is good, and car hire is affordable (you won't need a 4 wheel drive), but even so, I would strongly advise against driving between Cape Town and Kruger, which would take you at least 1.5 days and leave you exhausted.