When my son needed more fiber in his meals, I started grinding organic flaxseed, chia, hemp protein and psyllium husk into a powder fine enough to disappear into mac and cheese, a fast food taco, or whatever he was already happily eating. 

No taste, no texture, no fight. So now I blend it in small batches here in Longboat Key: four organic ingredients and nothing else. You don't have to change what you eat, just what it does for you.