Hi  – I personally pack my immune boosting supplements when I travel just in case someone falls sick. I don’t use them preventatively, but only if someone begins to feel sick.
 
• IAG (arabinogalactans), vit D, A, zinc
• ADP (emulsified oregano) & propolis spray for sore throats
• Silver hydrosol for immune support, ENT infections
• Plus some homeopathic remedies like Oscillococcinum for flu, arnica, nux vomica for plane nausea. I also bring homeopathic magnesium salts 

You can find the majority in my guide here with explanations of how I use each one.

In terms of prevention, ensure their immune nutrients are optimal (vitamin D, A and zinc). For kids who can swallow capsules, cod liver oil is an excellent source of vitamin A, D and omega-3. If they’re eating meat regularly, they are probably getting in enough zinc through food.

Some people like to take vitamin C and echinacea preventatively. I personally haven’t had the need for my family. 

What I do like to take on the plane is Cistus Incanus tea. I buy the ones in tea bags and plop one in each of my kids’ water bottles on the plane so they stay hydrated while drinking this herb. Cistus Incanus has been shown to stop viral replication, so it’s a good preventative herb.

The best prevention however is to avoid what weakens the immune system; overindulging in sugar, desserts, alcohol, stress/lack of sleep, etc. All of which usually increase during the holidays. So just keep that in mind without worrying too much and missing out on the joy of being with family and being out of routine.

Safe travels!