Your second approach should be to give your kid a sponge or lukewarm bath. Water evaporation leaves the skin cool and brings the fever down. It's not a good idea to use cold water for this purpose. Cold water will make your kid shiver, which may increase his fever further. In the same way, it's not recommended that you use rubbing alcohol either as it may cause alcohol poisoning or temperature spikes. https://fitose.com/healthy-keto-nation/