The Grand Traverse Band of Ottawa and Chippewa Indians enacted the change Wednesday at Leelanau Sands Casino in Peshawbestown, north of Suttons Bay, and Turtle Creek Casino, east of Traverse City.

More than 100 customers had complained about age restrictions since May 1999, when Leelanau Sands opened a 1,000-seat auditorium, the second-largest in northern Michigan. Such acts as Tonic, Billy Idol and Martina McBride -- which appeal to younger audiences -- have performed.

A number of complaints came from Detroit-area residents vacationing in the resort region, said Mark Belanger, director of marketing and entertainment for Traverse Bay Casino Resorts.

"We listened to our guests," Belanger said. "This decision is driven around entertainment. It has nothing to do with the Detroit casinos."

Several outdoor concerts also are staged annually at Turtle Creek Casino, including a popular blues festival.

The casinos have tightened security to ensure minors do not consume alcohol. Belanger said he expects most 18- to 21-year-olds to come for entertainment, so the move will have little effect on gaming attendance.

All patrons at Detroit's two casinos must be 21 under state law. Michigan's nine tribes, which operate 17 casinos statewide, set their own entry ages, though compacts mandate a minimum of 18.

Only three tribes -- Saginaw, Hannahville and Lac Vieux Desert -- allowed 18-year-olds on gaming floors as of September, the latest figure available, said Nancy Horton, spokeswoman for the Michigan Gaming Control Board.

Visits at the two Traverse City-area casinos dipped by about 110,000 when gaming arrived in Detroit last year, but normal numbers -- about 2.3 million people per year -- have resumed, Belanger said.