I get the same question from acquaintances every year--"So, do you let your kids eat Halloween candy?" My answer, "YES!" It's Halloween! I let the candy stay in the house for a couple of days, then it's gone. I make sure they are eating healthy meals on Halloween, so it's ok for them to have a few sweet treats. They also eat cupcakes at birthday parties, and they go the the team party that has pizza and snow cones--and they enjoy themselves. That is all a part of being a kid that I would not take away from my kids, nor do I stress about all of the artificial YUCK they are consuming for that brief period of time. Here's why: All of the other 345-ish days of the year (no, that's not an exact number, but you get the point), they are eating clean, whole, nutrient-dense foods and drinking lots of good ole Memphis water to keep their little bodies healthy and strong. Our bodies are in a constant state of doing a tremendous job of "cleansing" out the not-so-good-for-us things on occasion when we eat healthy, whole, clean on a regular basis. The kids have had their usual, healthy meals and snacks surrounding the party or trick or treating, so the they don't even want to eat too much. Unhealthy foods are not nutrient-dense. So, when the unhealthy goes in, I just make sure all of the healthy, nutritious food has gone in FIRST. Then, they can naturally moderate themselves....for the most part (they are still kids, afterall).
The bottom line is this: you need to decide for yourself where you want to draw the line with certain foods and how often you choose to eat them. Remember, it's all about your overall habits and lifestyle. Just as a person who eats a fast food-filled, overly-processed diet will not suddenly become healthy if they decide to eat a handful of blueberries, someone who generally eats a nutrient rich diet will not destroy their health with the occasional cookie.
You are the only one who can truly answer the question, "Is your definition of moderation keeping you from reaching your health, nutrition, lifestyle, and fitness goals?"