Humorist Robert Benchley said there are two kinds of travel–“first class, or with children.” But that distinction is fast disappearing. With more money, more energy and more leisure time than ever, growing numbers of grandparents are traveling with their grandchildren, says Tom Frenkel of the National Tour Association, and many join escorted trips. The idea is “definitely catching on–for several good reasons,” says Dorothy Jordon, publisher of the newsletter Family Travel Times. “Many children get 12 to 18 weeks of vacation a year. Their parents generally don’t get that much.” What’s more, grandpararents often live in distant cities and rarely get time with their grandchildren.

A handful of agencies offer tour packages specifically for such travel companions. Vista Tours of Carson City, Nev., takes grandparent/grandchild groups to Mount Rushmore, a Texas guest ranch, Washington, D.C., and Disney World. R.F.D. Travel Corp. of Mission, Kans., also tours the nation’s capital, and plans a trip to the Rose Parade this winter. The pioneer in the field is Grandtravel, a division of The Ticket Counter, in Chevy Chase, Md. Now in its fourth year, Grandtravel sponsors 21 one-to two-week tours to such places as the Netherlands, Italy, France, Kenya, the American West and Alaska. The trips are pricey: 15 days in Italy, for example, costs $2,895 for adults, $2,790 for children. But founder Helena Koenig notes that many grandparents plan to leave money to their grandchildren anyway. “In 20 years, that money will buy very little, and the grandchildren probably won’t remember where it came from.” Instead, the two generations can enjoy an unforgettable trip together. And, says Koenig, “this is an opportunity for young people to see that getting old isn’t so bad–Grandma’s having a great time.” Grandparents, for their part, like the idea of caring for a child again, particularly when they don’t have to do the dishes.

To date, Grandtravel has had a success record any camp counselor would envy: in four years, only one grandmother has gotten sick on a trip, and no one has been sent home for bad behavior. In fact, 75 percent of its customers come back again. There’s always a complainer, of course; last year, one 13-year-old girl stood at the edge of the Grand Canyon and declared it boring. “We pushed her over,” Koenig deadpans. “Not really. We told her she could go home if she wanted to, and her attitude changed immediately.” Mostly, the trips are filled with priceless moments. Koenig recalls that one little boy stood at the Grand Canyon with his newly widowed grandmother. She put her arm around him and said, “Granddad and I always dreamed of seeing this together.”

Grandchildren can make ideal escorts for single older women who want to see the world. “When I was first widowed, I thought that was the end of traveling,” said Flora Carlberg, 61, accompanying her 13-year-old grandson on a Grandtravel Western Parks tour last week. Now she hopes to take each of her nine grandchildren on a trip, one at a time. Another group touring England and Scotland last week, with stops at Buckingham Palace, Stonehenge and Beatrix Potter’s home, included grandmothers Viola Friedmann and Carolyn Ducote, neighbors in a Jacksonville, Fla., condominium. They shared one room; their granddaughters Holly Krull, 12, and Caroline Long, 13, shared another. And though they’d never met before the trip, the girls became fast friends. Their only complaint: “We wish there were more boys!”

No surprises: The energy levels of young and old don’t always match. To bridge the gap, each Grandtravel group includes an escort assigned to provide extra activities for the kids. And no one minds if anyone wants to sit out part of a trip. Last week in the Tetons, Frieda Kaplan, 70, chose not to brave the river raft. But there were plenty of other grandparents to look after her granddaughter Katie, 9. “This is great for someone my age,” says Kaplan. “Everything is planned.”

When the raft trip was over, the group enjoyed a picnic lunch, a tour of an Indian museum and a tram ride 11,000 breathtaking feet up a mountainside. After a comfortable night in Jackson Hole, they left by motor coach for Yellowstone. “We could use a fax machine on this bus,” quipped Joe Rault, a New Orleans oilman who, unlike most of the traveling grandparents, is not retired and searched for a phone at every stop. The group then took a walking tour through Yellowstone’s geysers, lunched overlooking Yellowstone Lake and rode a horse-drawn covered wagon to a cowboy cookout. “Our children keep reminding us that we never did this for them,” laughs Bonnie Rault, 58. “But they’re pretty tickled that we can do this for their children.”