It never hurts to shock a pool. With no stabilizer in the pool, it's easy to let the chlorine drop to zero and not realize it, which invites algae to grow. There are many reasons for cloudy water, but impending algae bloom is one of the biggies. Shocking the pool will stop that. You might also consider increasing your filter/pump run time a little and see if that helps--if it is sunscreen, then your filter needs to be running long enough to get it out of the water. I have no idea why they told you not to run the pump with people in the pool--people never get in my pool except when the pump is running!!

Janet