Toast the English muffins while you preheat your broiler and mix up the tuna.
Line a small baking sheet with foil for easy cleanup and put the toasted muffin halves on it, then divide the tuna among the muffins and spread out.
Top the adult portions with capers. Top each muffin half with a good slice of Cheddar cheese. If you added capers to any, add a caper or two to the top of the cheese so you can tell which have capers in them after they're cooked!
Slide under the broiler for a few minutes, until the tuna is warmed and the cheese is melted.