My kids are very very fussy, picky eaters and so prefer to drink liquids so I cannot escape giving them milk-based liquid meals. They need the nutrition that dairy provides. They just won't eat solids readily and do so a dairy-based diet is necessary. As for the mucous, well it is what it is. They will have less mucous once they are feeling well. Inflammation and mucous go hand in hand.

I am not particularly concerned because life is a cycle: sickness follows periods of well-being and vice-versa.