As to the ATS flow restrictions and needs for slots - a lot of these have been taken already - suggest you as a matter or urgency send your flt details to
[email protected] or check the web-site
ATNS and if you leave it to tomorrow it is going to be to late. DO IT NOW whilst there are slots avail and also slots avail for changes.
CJ750 GA is not screwed - if you do your planning now. Your bosses are going to have to be told in no uncertain terms to do their planning now and you are also going to have to express on them the need to stick to their plans.
Remember PROPER PRE-PLANNING PREVENTS PISS POOR PERFORMANCE and get in now before it is too late - dont do the standard South African thing - leave it to the last minute of the last day.
Gulfstreamaviator : seriously good FBO at FALA - EXECUJET - contact them for local details - they also got a branch @ FACT and handle a/c around most of SA. Check their website for contact details. Signature Flight Support, based at FACT can also help you there, check their website as well for details. Use these 2 FBOs and you wont go wrong.