To help boost the immune system of young children, focus on non-pharmacological measures such as ensuring they consume plenty of fruits and vegetables, get enough sleep, and manage stress effectively. Additionally, maintain good hygiene practices like avoiding close contact if someone in the household is sick, not sharing towels, and washing hands frequently. For prevention of colds, consider using a saline solution like Hydrasense or Sinus Rinse to cleanse the sinuses. This can help prevent mucus buildup and reduce the frequency of colds.