JOEL - Whenever possible we can privately instruct nonmembers that they need not partake of the sacrament, however, it is a general policy to not refuse them if they want to do it. It is not appropriate to risk insulting a visiting nonmember by refusing it to them. They may have their own personal reason for taking the Sacrament, perhaps related to their worship of Jesus and His sacrifice for us.

The Church Handbook says:
"Although the sacrament is for Church members, the bishopric should not announce that it will be passed to members only, and nothing should be done to prevent nonmembers from partaking of the sacrament." (Church Handbook of Instructions, 1998)

Because children under 8 years are innocent of sin it is always appropriate for them partake if they want to.