Mike,
9 or 10 days does give you plenty of time but the travel distances are large so would take up some of that time and adds cost. Especially internal flights and land transfers can add up, so see what is included. (e.g. you can fly CPT-JNB-Kasane to do Chobe and the houseboat/river cruise but that would miss out Vic Falls.)
If you are only using the train journey CPT-JNB as 'down time' then I would instead consider spending a day and night in the winelands around CPT relaxing with good food and wine with mountain vistas before flying early morning to JNB the next day - the timings would be similar and SA is great value for money for food and drink. I could easily spend all 9-10 days around the Western Cape region (note it's the Cape of Good Hope or Peninsula).
One issue may be organising the dates / availability if you are booking so late for the river boat and for the train because they only leave on certain days (although Oct-Dec is lower season - CPT will be lovely but Chobe / Vic Falls will be hot). IMO, you get the most from safaris if you can overnight within the parks. It is a general rule that predators are best spotted in the first few hour(s) of daylight.