I can highly recommend Ngala Private Game Reserve. It's not in Sabi but instead is in Timbavati, and is also contiguous with Kruger. They have a few family rooms which will accommodate 2 adults and 2 kids.
We stayed there in 2015 with our two kids then aged 12 and 10 and we all had an awesome time. Our ranger really looked after the kids well - they went searching for bugs, made plaster casts of animal tracks, etc. They also had some fun baking cookies in the kitchen and played soccer with some of the children of the staff who live nearby.
We've also stayed in the Singita properties in Sabi - I think Ebony has a family room, but Ngala has much more of a family vibe.