The President may enroll in the Peace Corps qualified citizens or nationals of the United States whose services are required for supervisory or other special duties or responsibilities in connection with programs under this chapter (referred to in this chapter as “volunteer leaders”). The ratio of the total number of volunteer leaders to the total number of volunteers in service at any one time shall not exceed one to twenty-five. Except as otherwise provided in this chapter, all of the provisions of this chapter applicable to volunteers shall be applicable to volunteer leaders, and the term “volunteers” shall include “volunteer leaders”: Provided, however, That—

(1) volunteer leaders shall be entitled to receive a readjustment allowance at a rate not less than $125 for each month of satisfactory service as determined by the President;

(2) spouses and minor children of volunteer leaders may receive such living, travel, and leave allowances, and such housing, transportation, subsistence, and essential special items of clothing, as the President may determine, but the authority contained in this paragraph shall be exercised only under exceptional circumstances;

(3) spouses and minor children of volunteer leaders accompanying them may receive such health care as the President may determine and upon such terms as he may determine, including health care in any facility referred to in section 2504(e) of this title, subject to such conditions as the President may prescribe and subject to reimbursement of appropriations as provided in section 2504(e) of this title; and

(4) spouses and minor children of volunteer leaders accompanying them may receive such orientation, language, and other training necessary to accomplish the purposes of this chapter as the President may determine.