The other secret is to add collagen powder, which gives an extra protein boost without changing the texture or the taste. We have tried two and like them equally: Bulletproof and Z!nt, both of which can be ordered from Amazon.
2 cups plain yogurt
2 bananas, ripe but not too ripe
1.5 cups frozen fruit - our favorite combination is equal amounts of strawberries, blueberries, and raspberries, but we also like blackberries and mango
2 scoops collagen powder
I've found that the order you put the ingredients into the blender matters, especially if you have an older model like mine. I put the yogurt in first, then the frozen fruit (bigger ones like strawberries first), followed by the bananas. Blend until smooth, and then add the collagen powder and blend once more.
Yield: 3-4 medium to tall glasses
Try this and let me know how you like it, and what fruity combinations work for your family!