One of the things that brings me joy and is a testamate to kind approach to working with dogs I know and love, is involving kids in training. Here are a few ways that I ensure that kid's can safely be junior trainers too.
First, it's about the supervision, of both the dog and the child. Supervision doesn't help if the adults don't know how to interpret what they are seeing, so before teaching anything about training to a child or their parent, I ensure that they are both well versed in doggy body language. There are general canine signals that they give us to indicate if it is or is not the right time, environment or circumstances to train.
Second, start with basic interactions and build the child's experience from there:
Take a walk together; adult takes the leash attached to the harness and the child takes the leash attached to the flat collar. That way, the grown up has the control and the child has the experience and involvement in performing the task of walking. Depending on the dog, the maturity of the child, you can also give them a job which is to be the reinforcement deliverer during your walk, whereas they pass down the treat for the eye contact, loose leash, etc.
Fetch; start with the simple back and forth and then add on cues if the child is of the age they can give them correctly like sit-stay before throwing the ball or leave it if the dog is familiar with that one.
Games and toys; One of my favorite ways to get kids involved in their puppy's training is to encourage the family to play hide-and-seek to work on their recall. Have the kid(s) hide (difficulty on location depends on the skill/age of the dog) and call out using their pup's name or the recall cue. Then have them deliver the reward when they are found. You can also involve your child in stuffing kongs or preparing licki mats and delivering and observing other food toys and puzzles. Never leave children and dogs alone together and keep an eye on body language.
Clicker training; there are great books available that are written to help you involve your child in dog training. Specifically, for clicker training, I recommend practicing many clicker games without the dog present first to let them learn the mechanics - timing, treat delivery, etc. Also, I always ensure the behavior/trick is fluent before passing the cue along to my child to give to the dog. This way I don't run the risk of the dog being confused or frustrated and the cue being accidentally poisoned.
In my home it has been fantastic having my seven-year-old daughter understand the fundamentals of clicker training. It can be difficult to train my puppy and leave out my older dog. As my trusted Junior Trainer, I can rely her to work with my eldest Maci, while I get some one-on-one time with my youngest, Miles. She feels great pride in her ability to train and I cherish her skills and bond with our dogs too!
The pawsabilities are endless when you safely involve kids in training!