Hi
That is good if he took to the fruit juice. At least you can do variations in that. does not always have to be the same fruit. Mixing blue/blackberries might be a good one as well.
Slippery Elm usually comes in a powder form or like small chips. Youmight be able to get in tea form -- but it can be so weak that way. Just depends on the manfacturer.
Did the toodler has any kind of trauma? prior to this problem? the toddler might not be albe to express this but does he have a phobia about anything?
Mountian Rose is a good place to get oils and herbs generally. Very good prices on some things.
Ginger oil might be sticky to use by its self but put it with half teaspoon of plain oil.
If you are in UK Europe then Tissaurand is a good make.