The "kix cereal" you described sounds alot like some stones that I have passed, too. I will tell you what I found them to be, and then you can decide for yourself if yours are the same.
They always float, are creme colored, have a clay like consistency, and are rounded/oval in shape. Mine are much bigger than kix cereal, but have noticed some smaller ones recently. I began passing at least one a day, and it freaked me out! If something so unusual is coming out of my body, I am on a mission to find out what it is!
I found out that they are cholesterol stones from my gallbladder. The reason they float is because they are fat! Your gallbladder makes a mixture of different ingredients to aid your body in digestion. When a person fasts, or goes without food for a period of time, the gallbladder creates an imbalance of the mixture(because it's not being used). When it makes the cholesterol, and has no place to use it, the cholesterol hardens and forms into stones. The lemonade is flushing these stones out! SO, they are not dangerous or even waste from your body, just excess cholesterol that your gallbladder made that your body isnt using right now. The only problem could be if one of the stones were to become stuck in the canal that it travels through from the gallbladder to the small intestine. This hasnt happened to me...but I have been told it is quite painful.
I'm not a doctor, just wanted to let you know what my research discovered!