I just transitioned from whole to 2% last week, and DD is 2 y 10 m. She is very small and much of her fat and protein came from drinking the whole milk, however, for me, I made the decision based on $$$. My husband and I use 2%, so we were only buying whole milk for her, and I ended up tossing a lot. I just hated pouring money down the drain. I decided given that she only consumes about 10 ounces a day anyway, whole was just no longer worth it.