Place a glass bowl on top of a saucepan partially filled with water over medium heat. Add the coconut oil and cocoa butter. Melt
Carefully remove the bowl from the heat. Allow the mixture to sit in the saucepan for 5 minutes. This will allow the mixture to cool so the oils aren't damaged.
Homemade vapor rub will keep at room temperature for 12 months.
As always, please do your own research when it comes to using essential oils, particularly on young children. Using eucalyptus on young children may slow respiration in some children. Also, peppermint and rosemary essential oil aren't recommended for young children. Here's a handy post (as mentioned above) about kid ages and essential oil use.