I mean besides fruit, water, and beautiful greens. 

I often throw in salba seed or ground flax, and have been adding spirulina, wheat grass, kelp, or aloe vera gel lately (not all in each smoothie though!). I started sprinkling some powdered veggies in small quantities, but they don't taste as yummy if I put more in, as the flavor is a bit strong. I keep the amounts small, primarily because I make them for my kids as well. But I'm wondering what type of other nutritional enhancers others add. I'm also wondering if there are any nutritional guidelines with things like flax meal, wheat grass, etc. for kids.  Any input appreciated. 

We pretty much use the same things!

A staple around here is to add goji berries, chia seed, spirulina, chlorella, and aloe vera juice. We also often times add tahini or sesame seeds.

As far as I know there are no "nutritional guidelines" for kids. Pretty much any raw whole food that's good for you is good for your kids. Do limit wheatgrass though as it contains a relatively high concentration of alkaloids. Also go easy on spirulina if you use the dry form as we have witnessed our son have a hard time with it on his system when he was younger.

Continue to keep the amounts small as you try new things, build them up slowly and pay attention and things should be just fine.

Thanks. Will look into the goji berries and chia seed. Can I ask where you buy them? Online? Never thought about tahini! Sounds good.

Yep I buy them online.

Navitas has Organic chia and goji for a great price!