D.M.
Hi Heather,
My grandmother gave me the recipe of 1 cup of ammonia, 1 cup of dish soap, like Joy or Dawn, and one cup of water. It has worked for me in the past, by getting out grass stains, blood, food stains, etc. I hope you find something that works for you, I know how frustrating stains can be when you want their clothes to last, especially since they grow out of them so fast.
Take care,
D.