I'll add to Toni's great response. Beans, legumes are all other sources of great protein. Start with white beans, my daughter loves them with EVOO, white balsamic vinegar, salt, pepper and oregano. Black beans with salsa and an avocado is an excellent mix of fats, veggies and protein. :)
If you are interested in a protein supplement, I do give my 19m old daughter a vegan rice protein powder by Nutribiotics, it is organic and enzymatically processed meaning the beneficial enzymes have not been killed in the process as most are in other protein powders. I give one teaspoon per 3oz of rice milk (or milk of your choice); I've been giving this to her since 12m old, I add her fish oil and liquid multivitamin to it and call it her special protein shake. :) I do make smoothies with it for her and will enjoy them every now and then. the protein powder can be bought for about $13 at www.vitacost.com or www.vitaminshoppe.com I can find my daughter's liquid multivitamin at vitacost called ChildLife, which will be fine for your 6m and 6yr old. The tub of powder will last you a long time, unless you use some yourself, only 1T is needed for an adult (great to add in a bowl of cereal for the extra protein boost). I bet your little one will love a smoothie...especially if it tastes like a milkshake. I do have some kid friendly recipes on a word document I can email to you. (Sweet-tart Smoothies, PB and J smoothie, etc)
Remember, kids over 2 yrs need about 7g of protein in the morning to sustain blood sugar (adults 14g), and keep from wanting sweets later on. This is equivalent to about one egg, the protein powder will supply that for you as well.
J. W. MPH
Wellness Educator