Getting E. coli 0157 from a chlorinated pool is rare, but it can happen. Normal levels of chlorine in a pool kill this and other bacteria almost instantly. However, chlorine can temporarily become too low from the presence of many people in a pool using up the chlorine when sweat and other substances go into the water. If a child has an accident in the pool, the stool would both use up additional chlorine and may also contain dangerous germs. Fortunately, even when accidents happen, generally the stool contains no dangerous germs.
Children benefit from the enjoyment of being in the water.
This kind of outbreak is so rare, it is probably more dangerous to drive your children to the pool than to risk disease from the pool. Certainly, the risk of drowning in a pool is higher than getting severe illness from one. Children who are not toilet trained should be kept out of the pool. If very young children do go into the pool, they should wear secure plastic pants. Children with diarrhea should not be allowed in the pool.