Floridagal23 and Hawaino - I am sure you will both have an amazing trip to Singita Ebony and will really enjoy time on safari. I am an avid safari goer and after going on my first (once in a lifetime) trip in 2006, ended up going back another 3 times in 2008, 2009 and 2011. On my first trip we traveled with good friends and stayed at Singita Ebony as well as Skeleton Coast - Namibia, River Club- Zambia, Jao & Mombo - Okavango Delta-Botswana. I fell in love with Botswana on that trip and my 3 subsequent safaris have all been to Botswana (Jack's Camp 2x, Mombo, Little Mombo 2x, Duba Plains 2x, Kings Pool, and Duma Tau.
The others have given you great advice regarding binoculars. You should have a pair for each of you - because when you are spotting something in the distance (a leopard in a tree or a cheetah stalking in high grass) you will both want to be able to see. We invested in two lightweight pairs on our first safari - which were sufficient for our needs and have been used extensively. I liked the light weight versions because the heavy ones were just too uncomfortable to wear around my neck.
For camera equipment - it is critical that you have image stabilization on your telephoto lens. I actually ended up getting 2 camera bodies (digital SLR Canon) and had one set up with the telephoto lens and the other with the wide angle. This allowed me to change shooting angles without having to change the lens - very hard to do in the dust and quickly. My husband was content to shoot with the point and shoot and his iPhone and he actually got some really nice shots. There is plenty of room in the jeep for your camera bag and a tote bag to bring your layers of clothing.
For clothing layers - I would often find it cold in the morning and start out with a tank top, tee shirt, long sleeve button up shirt, fleece and windbreaker. I always would ask the guide to have a hot water bottle ready to keep in my lap. Additionally I had a knit hat and fleece gloves. It can be really quite cold for those early morning starts. However hour by hour the layers would come off and by the time you finish the morning drive you are hot and sweaty. Really good UV sunglasses, sunscreen and a wide brimmed safari hat with a chin strap are really necessary. You need the chin strap because when the jeep starts moving fast - hats get blown off pretty quickly. In the evenings - the first safari i brought nicer clothes to change into but after that - we would just shower and change into the next days clothes with the addition of a nice sweater and maybe some african jewelry bought at the great gift shop!
Regarding wild life spotting - learn to take it as it comes. There will be drives when there is more action than you can imagine and others that are more on the quiet side. However even when the drive is quiet - there is still so much to see. The guides are really amazing at helping you to see and learn so much about he environment and smaller creatures. I am not a birder - but gosh there are some very beautiful birds in Africa.
On jeep mates - I have only ever had one really bad experience and this person was so over the top that everyone at the camp was annoyed with her. The managers actually had to intervene and she was driven privately for the rest of stay. But that strange situation aside - I have met some really lovely people across all four trips. It is such a wonderful experience that I find most people are predisposed to be enjoying their time. If you do come across the unfortunate and unlikely situation of a difficult pairing - simply and quietly ask to speak to the camp manager and see if any accommodation can be made.
When we were at Singita Ebony in 2006, the lodge arranged for our husbands to have a private tasting visit to the cellar room at Boulders. My friend and I elected to use this time to sit in front of the fire in the Ebony lodge and relax. The men loved the tasting and arranged to purchase a number of the wines they tasted and have them sent back to the US.
The rooms at Singita are really lovely and large but since you are out on safari for large portions of the day you don't have a ton of time to enjoy lounging. Our friends opted to miss one of the drives so they could have a morning to relax in the room. This is an option that I have seen many take advantage of across my trips. I love the safari drives though and would never consider missing any - on that particular drive we ended up seeing a Mother and Baby Rhino and a cheetah kill an impala so they were a bit bummed they missed it.
They try and make memorable moments for you on your trip there as well. One night they set up our sundowners out in the bush with a fire and a buffet and bar, a portable WC and a tree lit with lanterns. It was magical and we were all enjoying ourselves until one of the guides came in and calmly told all of us including the staff to make our way to the vehicle. There was a pride of 20 lions about 200 yards away - beginning their nightly walk to their hunting grounds. So with cocktails in hand we headed out in the jeep to follow their progress - very exciting!!!
Have an amazing time - I envy you both!