use of histinex hc syr in 2y/o with croup

36# 4y/o was just diagnosed with having croup today. dr suggested giving dimetapp cold&cough and drinking lots of fluids and tylenol only if > 102 F.

started off w/ vomiting and fever last Thursday & Friday nights (while sleeping). still has fever today, Tuesday. Started w/ cough Sunday; vomited only saliva Monday. Have been trying to treat w/ ibuprofen & acetaminophen for fever, benadryl @ bedtime and delsym for cough, and vaporizer at bedtime. Constantly coughing while asleep. no appetite.

dimetapp cold&cough has antihistamine, decongestant & cough suppressant. any reason not to ask dr for rx of histussin hc at bedtime so child can get decent sleep @ night? keeping child out of pre-school for now--missed 2 days already.