A note to the OP - SAA officially joins Star Alliance in April, so your United miles can be used on several different carriers to get to SA - Lufthansa, SAA, or even Singapore Airlines (who serve JNB via SIN.) So while it's a good idea to book ASAP, you could also ask UAL if the same advance window rules (outbound minus 330 or inbound minus 330) apply to those carriers as well. Some carriers will allow FF booking farther out than 330 days, although usually only for their own members.

If you plan to go for business class, most carriers' business cabins are heavily booked by paying pax to SA, so the earlier the better in terms of reservations. Unlike flying in economy, it's more likely you'll need to alter your safari booking dates in order to have it work with your fly dates, as you'll need to take the flying dates they give you.

Certainly get the flights first. June / July is low season in SA and you;ll get a great choice of accomodation even a few weeks before you go ...

Hi Merrittm
I would hesitate about booking a confirmed safari with deposit until I had my flights. I don't know anything about how CCAfrica works, but we booked a private safari with Africa Dream Safaris and they worked around our air. We're using AA rewards and flying the London/Nairobi leg business class on BA :) and our layovers are minimal. We did all of this only 6 months before our trip (May 28 - June 11).Also, ADS was very laid back about getting our deposit, so we had plenty of time to work out the air and hold our lodge reservations with ADS without the worry of losing a large deposit. Good luck!