Suggest Treatment For Sore Throat Along With Swollen Lymph Nodes In A Child

My 3 1/2 yr. old grandson has been ill for over 2 weeks with sore throat, very swollen glands and tonsils, elevated white count and platelets, low iron. First thought to have mono, but bloodwork negative. Fever is gone after first week, but neck glands worse. Now stiff neck too. On antibiotic for past week. What type of specialist should we be thinking of? Pediatricians just keep saying its viral and wait longer.