M.R.
Unless he is getting a life-threatening disease, take him. What are you going to do when he goes to kindergarten and is around 24 other kids who sneeze, touch each other, don't wash their hands after going to the bathroom, and come to school sick? While I would never suggest that someone purposely expose their child to an inordinant amount of germs and viruses, I think that what your child wants to do is 'normal' and part of 'growing up'. Being in his house in a sterile environment has not really given his immune system a chance to build up any resistance.
At the same time, you really do take your chances when you drop your kid off at a babysitter like in Bally's. Those places typically are not licensed by the state and the caregivers may have had zero training in child care or safety.