For the second straight year, Gov. George Deukmejian vetoed a bill to require group insurance plans to provide preventive health care benefits for children, such as checkups and shots. The bill was carried by Assemblyman Louis J. Papan (D-Millbrae), who said he will try for a veto override. The governor said the bill would increase health care costs, drive more employers into the self-insurance field, set a precedent to mandate other costly insurance coverages such as acupuncture, alcoholism, and home health care, and create another hurdle for attracting new business to California. As it went through the legislative process, Papan argued that the bill actually would save money by early diagnosis and treatment of children.