I feel for you! My mom is somewhat that way too. I'm also from Malaysia (assuming that's where you are from given your username) and we will be traveling with my 1.5 and 3.5 year old in January from SFO to KUL. I would not worry too much about being flu/cold season. Planning to vaccinate my kids against the flu, and lots of proper hand washing during the journey. I'm also planning to wipe down the arm rest and tray tables. Make sure to bring a water bottle to keep hydrated during the flight. Kids will get sick several times a year anyway regardless of what you do, and I don't think this will be the sole reason to not travel.