Hi.. Thanks for the query.. It looks like your son is suffering from a viral infection causing high fever and rashes and white coating on tongue is due to fungal or yeast infection known as Oral Thrush.. Many a times when there is any infection in body and the body s immunity is low then opportunistic organisms like Fungus overgrow rapidly.. This is the cause of white coating on her tongue. Along with medication for nausea you should also give her acetaminophen for fever reduction.. Also get a blood test done to rule out the exact nature of infection and if needed antiviral medication can be advised.. Apply Calamine lotion to soothe the skin over the rashes.. You can also put Candid mouth paint over her tongue so that the fungal infection subside.. Also give her plain yogurt as it is probiotic and helps in reducing the white coating faster.. Maintain a good oral hygiene.. Hope this helps.. Regards.