Start by adding your rolled oats to the food processor and pulsing them until they resemble a coarse flour. This step only takes about 20 seconds, so don't walk away or you'll end up with oat powder instead.
Add the whole wheat flour, baking powder, and salt straight into the processor with the ground oats. Pulse everything a few times just to combine, which keeps the dry mix light and evenly distributed.
Toss in your freshly grated cheddar and cold cubed butter, then pulse again until the mixture looks like coarse crumbs. The cold butter is what gives these crackers their crisp bite once they hit the oven.
With the processor running, slowly stream in the cold water one tablespoon at a time. Stop as soon as the dough clumps together into a ball, since too much water makes the dough sticky and hard to roll.
Place the dough between two sheets of parchment paper and roll it out until it's about an eighth of an inch thick. Use your pizza cutter or cookie cutter to slice the dough into small squares or shapes the kids will enjoy.
Transfer the cut pieces onto a lined baking sheet and bake at 350°F for about 12 to 15 minutes. Pull them out once the edges turn a light golden brown, then let them cool completely so they crisp up fully.