Just my opinions. Yes Sabi Sand lodges restrict to 3 cars at a sighting. Thanda may be fewer I don't know. I did find the lodge we went to in Sabi Sand a bit commercialised and the drives very focused on cats. While very nice to spend time with leopards it didn't feel as 'authentic' and unknown as other drives in other private reserve lodges we've been to. e.g. in Klaserie reserve we've had trackers determine the movements of a lion pride over several days and we got a great sighting as a result, initially just us and then one other car was called in. But we did see 'less' cats and more 'interesting' chameleons and the like. Anyway I am not the most knowledgeable, as we mostly self drive now, hence a good safari agent can help with finding family friendly places that suit you.