The oils that I use and love are doTERRA, but feel free to use any other high-quality oils you like to help your child cope with their worries. I really like the Kids Oil Collection because it comes with six different blends that are premixed with coconut oil. My kids love layering them and they feel more in control of their desired thoughts. I also use them! Visit this link and search for the kids oil collection to get started.
(Full Disclosure: I will receive a commission if you choose to purchase oils using this link)