Peel and finely chop the onion and garlic and put them into a medium bowl.
Put on a pair of kitchen gloves. Rinse and cut open the pepper. Remove all of the seeds. Finely chop the pepper and add to the bowl. If you want REALLY spicy guac, add two peppers. If you want mild guac, only add half.
Have your kid rinse the cilantro and tomato. Finely chop and add to the bowl.
Have your kid squeeze lime over all of the ingredients. Add the salt. Set aside.
Cut the avocados in half and remove pits. Carefully cut a criss-cross pattern into the flesh of each avocado. Have your kid use a spoon to scoop the avocado out of the shell and into a bowl.
Have your kid use a potato masher or a fork to gently mash the avocado chunks. Do not overmash.
Add the avocado to the other veggies. Gently stir. Serve with tortilla chips.