Child with 101.9 fever for 3 days, a lot of mucus, rosey red cheeks and nose, and congested cough. What is it and what to do? Now please.

Viral. Fever control, make your child comfortable. You may give decongestant/expectorant, antihistamine to help with the mucus. Have your child see doctor to rule out underlying bacterial infection eg sinusitis, tonsillitis, ear infection, pneumonia. Also wants to be sure, it is not fifth's disease.
Likely simple cold. Most likely, a scenario like this represents a simple viral cold. This time of the year, our office is packed with similar cases. The problem is, that this is likely viral and therefore antibiotics i'll not help and there is nothing else to make this go away except time and normal immune function. Motrin and a nice hot steamy shower to get the snot out, especially before sleep should help a lot.