Nothing can ruin a good day outdoors faster than ill-fitting or unsuitable footwear. That goes for kids trail shoes just as surely as it does for grown up mountain boots. If children are wearing shoes that let them go where they want to go without pinching or their feet sliding around inside they'll feel more comfortable and more secure, and get the most fun from their outdoor activities. Not only that, but you'll get a much more peaceful day if they're not hopping around!
For casual, short hikes all kids outdoor shoes really need to do is provide a little bit of support and cushioning, and have a nice grippy sole for security. That last point is important, particularly if your kids are the type of go-getters that love to run around and explore but might not always be on the lookout for slippery surfaces or loose ground. As children get older and start to be more capable of longer, more challenging hikes and other outdoor activities, they should have outdoor shoes that are just like mom and dad's. Their footwear will need to provide contoured arch support that'll help them beat fatigue, it'll need to be waterproof, and it'll need to fit well. To test for a perfect fit, feel the front of the shoe. Their toes should be about a little finger's width from the front of the shoe. At the back, you should just about be able to slide the same finger down the back of the heel without a struggle.