As alumni of a bygone era descend on their alma mater this week, their offspring will spend five days frolicking at Camp Harvard.

At the 25th reunion these lucky kiddies are treated to movies, dances, picnics, and museums--at no extra charge to parents. Fathers attending their 25th Harvard reunion will pay a flat rate for the entire family to participate in a five-day extravaganza of activities.

About 1000 children of members of the Class of '61 will be divided up into five groups--Blue, Orange, Green, Red, and Grape--according to age, said Marion R. Briefer, associate for major reunions.

The youngest children--ages six to nine--in the Grape Group will spend their evenings watching the classic movie "Willie Wonka and the Chocolate Factory," viewing mime and magic acts, and being entertained by a puppeteer. Their days will be filled with the Big Apple Circus, roller skating, bowling, museums, the zoo, and a special trek to Walden Pond.

Nicholas M. Snow, six years old, is coming to Harvard with his parents and two older brothers. He was too shy to be interviewed, but his mother, Sara E. Snow, said, "He wants to go bowling. For him it will be like a five-day birthday party."

Meanwhile, the oldest offspring--18 and older--in the Blue Group will be participating in such exciting pastimes as symposia on "Harvard Today," "The Lively Arts," "Our Economic Environment," and "After College, What?" They can also spend their time playing golf and tennis and drinking--provided they're wearing wristbands signifying they are at least 21.

The Blue Group will also watch the teen-age-growing-pains film "Risky Business" one evening. Other nights will be occupied with dances at Lowell House and at the Boston discotheque The Metro.

"It should be interesting to go to the Metro with my parents," said Stephanie H. Roth '89, who is coming back to Harvard for her father's reunion. "I've never gone out dancing with them."

High school age children in the Orange Group will also have the chance to dance nights away at the Metro and at Eliot House.

The Orange Group--aged 15 to 17--have the varied schedules, enjoying the sights of the Boston area and learning all about their parents' alma mater. They'll spend part of the week shopping at Quincy Market, hiking at Mt. Monadnock, swimming at Crane's Beach, and cheering on the Boston Red Sox. But on Wednesday afternoon they'll have the opportunity to attend symposia on "Inside College Admissions" or "Life at Harvard."

"We don't have to recruit them," Briefer said. "Once they get here, and they have a good time, we don't need to."

John A. Ten Brook Jr., who is a sophomore in high school, said he already wants to come to Harvard. In fact, he said he left prep school early and will have to take exams late so that he could attend the reunion. "I really didn't want to miss exams, but I'm looking forward to it because I've heard everybody talking about it," he said, adding that he's most excited about going to the beach and the Red Sox game.

His father, John A. Ten Brook '61, said, "Remembering from my undergraduate days what a big deal it was, I didn't want them to miss it."

The Green Group--13 and 14-year-olds--and the Red Group--10 to 12-year-olds--will watch the cycling film "Breaking Away," go to the circus and the amusement park, go roller skating and to the beach, and have their own dance parties.

And everyone agrees that one of the week's highlights will be Monday night at the Boston Pops at Symphony Hall. The traditional event is offered to all but the youngest children, the Grape Group.

The week will culminate, of course, with Commencement. But only the oldest children, the Blue Group, will be able to accompany their parents to that event. The younger children will be shipped off to the beach and the zoo.