if afraid the orange, you can use pear.
my son 4 years old and it's work for him.
may be not because of the pear or orange, but the most important is 川貝, you need to buy better 川貝. cheap one does not work. I usually buy at around $50 and can share to cook for around 4 to 5 times.
and separate to eat 3 times a day for each cook.
may be they always has hot cough and thus 川貝 work.