Kids can get sick if they don't learn good hygiene habits. Bad hygiene creates a breeding ground for bacteria and viruses. They thrive in dirty, unkempt conditions. Many of the recommendations that doctors give children during cold and flu season have to do with hygiene. For example, children are told to cover their mouths when they cough and wash their hands regularly. Doing these things can help with killing germs and preventing them from spreading from child to child.
If you are thinking about an activity you can put your child in that will give them a lot of great benefits now and in the future, then you should think about having them take guitar lessons. Of course, you do want to talk to them about this and see how they feel. You don't want to force them into learning how to play an instrument they have zero interest in, or they will end up quitting as soon as they can and never look back.