MGM GRAND AIR, an all-first-class transcon-tinental airline for the executive business market, begins service Sept. 8. It aims to restore true first-class standards at competitive prices. MGM Grand Air will fly twice daily between Los Angeles and New York. For reservations contact a travel agent. FAMILY CAMPING WITH THE BOY SCOUTS is now offered at more than 180 Boy Scout camps in the United States, the Virgin Islands, Canal Zone, and Puerto Rico - at budget rates. One family member must be registered with Boy Scouts of America. Locations and dates (most are open year-round) are printed in Scouting Family Camping Directory No. 3680A, sold at Boy Scout Council offices for $3.20. Or call 800-323-0732. A RECORD NUMBER OF VACATIONERS HAVE TOURED THE UNITED STATES this summer, according to the Travel Industry Association of America. The travel boom is fueled by American vacationers and foreign visitors taking advantage of favorable US dollar exchange rates. SCANDINAVIAN TOURISM IS ON THE RISE. According to the Scandinavian National Tourist Offices, there has been a 27 percent increase in telephone inquiries and a 65 percent increase in the number of visitors during the first four months of 1987 compared with the same period last year.