Spectacular and very long: the wildlife is the easy part, and the six-hour road in and the open-ended waits at river crossings are not.
Distance is the problem, not the animals
Five to six hours of rough road each way from Nairobi, then two long drives a day once you arrive. Flying from Wilson in about 45 minutes is the single biggest improvement you can make to a family trip here; the strict light-aircraft baggage limits are the price of it.
Family rooms in the Mara Triangle
Mara Serena has eight sets of interconnecting rooms, a heated pool and buffet meals, with Maasai dancing three evenings a week — the practical end of the reserve for families rather than the romantic one, and the only lodge inside the Triangle.
Camps are unfenced
Most Mara camps have no perimeter fence; guests are escorted to their tents after dark by Maasai askaris and nobody walks about alone at night. Ask camps directly about minimum ages before you book — they set their own and they vary a lot.
The middle of the day is yours to fill
Drives run at dawn and again from about four; the four or five hours between are hot, flat and empty of wildlife. With children, a camp with a pool is worth paying for, because that is precisely the part of the day you have to survive.
River crossings need more patience than children have
Waiting on a bank for wildebeest that may or may not cross can take an entire day and frequently ends in nothing at all. Either manage expectations first, or base yourselves in a conservancy where the drives are shorter and the sightings closer to camp.