would you bring a 4 month old to disney

Is that too young to take a 3 hr plane ride and then stay a week in Disney? It's in December so the weather would be mild, and not too hot. We are just worried about him getting sick. The reason we are so heavily debating is because we didn't take a honeymoon, and my family is going (about 20 people) and we really don't want to miss out!!