Carry out a risk assessment to see whether or not a higher level of protection is required for these individuals. Factor in the frequency of contact between individuals, surfaces, etc., as well as the type of work. You may also factor in other controls in place (hygiene procedures, physical distancing, etc.), to justify whether or not a higher level of protection is needed.
Face shields can be used in the workplace in combination with face masks to provide added protection. They cannot be used to replace face masks or other protective measures.