Complex sentence: These cards are swapped with other "russ" and handed out to children or family members; for many children, collecting huge amounts of "russ" cards is an important activity during May, culminating on May 17.
Split into simpler sentences: These cards are swapped with other "russ" and handed out to children and family members. To many children, collecting "russ" cards is an important activity during May, culminating on May 17.