In all honesty I try to not give kids medication when it is not for their age group. All the kids dying from meds that were not meant for their age group is just one of those things that reinforces it to me.
I would ask the doc for a nebulizer and some Xophenex. The med is mixed with sterile water in the vial and it loosens the goo about the same to me. It also helps the goo come up easier that the tussin.
I am using tussin, sudafed, and the nebulizer to keep all my symptoms at bay.