Like tools or clothing?
We have 3 kids. Each of our jeeps has an emergency kit with fleece clothes for all and extra food, medicine, and water. It also includes signaling devices, etc. It's more for if we went off the road or broke down and had to stay put for awhile while waiting for help. I built these kits myself as I couldn't really find anything decent that was prepackaged at a store.
As far as trails, we carry a ton of stuff and tools for vehicle repairs (different kind of kit). We also seldom wheel alone, and if we do, we always tell someone where we're going and when we plan on being back. There's no cell service where we go, so we find this step important.