Hi LinS
This is a new trip for JY with the first date being for next month so there are no specific reviews as yet. I am booked for this in November this year. I usually post a review so watch this space.
At present there are no specific vaccination requirements but it is always to check with your doctor re any specific needs or updates you may need. There are currently no visa requirements for British passport holders but check if you are travelling on any other passport.
I have travelled to both SA & Kenya with JY in the past and reviews for both trips are on the review page. The Mabula reserve has both web pages and a Facebook page you might want to check out / follow. It gets good reviews on Tripadvisor.
There are no guarantees about sightings, animals can be very fickle, but drivers are usually very good and in touch with each other to give visitors the best experience.
Muted colours are best on safari and pack warm clothing as July is their winter and it can be cold early morning and breezy whilst jeeps are moving. A wide brimmed hat is good - with a chin strap as should it blow off you can't hop off the jeep to retrieve it!
Also the SA electrical adaptor is unique to SA so I suggest you get what you need before you travel - they are on Amazon (other sites are available). As regards shopping I don't know what opportunities there will be at Mabula but J'borg airport has some good high end shops - they take cards!
Anything more specific then feel free to ask.
Happy sightings
Ian