Using some baby Vics rub on his chest too will help. And I stand by a warm mist vaporizer works better then the cold in these instances, but that might just be me.
My daughter is 1 right now and is also sick and it's so hard-I know!
Since he's already on meds your big concern should be dehydration. If he's at least taking fluids you are good-don't worry if he's not eating.
Also-give him yogurt juice or yogurt or a probiotic, etc to help off set the antib issues that he's going to have with his system.