The More, The Merrier

If you think planning a vacation is difficult, try organizing one for a family of 14. That's what Helga Knox, 54, did last year for her husband, George, three of her stepchildren and their spouses and six stepgrandkids. They splurged on an eight-day, small-ship cruise through Alaska's Inside Passage, debarking to hike, raft, kayak and--the trip's highlight--ride a helicopter to stand on Juneau's 7,000-foot Mendenhall Glacier. "It was the perfect trip," says Knox of last July's adventure. "I just get excited about it whenever I think of it."

Families like the Knoxes make up one of the fastest-growing segments of the travel industry. In 2003, 38 percent of family vacationers took at least one trip that involved three generations, up from 19 percent in 1999, reports the Travel Industry Association. And travel agents say the number of large family groups going away together is still rising. "Five years ago I didn't do any of this, and now each year we're doing more and more," says Patty Jefferis of WhirlAway Travel, based in West Chester, Pa. ( ), who booked the Knoxes' tour. The growth in intergenerational travel is fueled by baby boomers who, like Knox, love to travel and have the discretionary income to take their kids and grandkids with them.

Adventure is just one benefit of such a journey. Knox, who chose the Inside Passage cruise from Tauck (from $4,490 per person; ), decided to book the trip after her husband, George, 79, began showing the first signs of Alzheimer's. "We all know what's going to happen with the illness down the road," she says, so she wanted to give her kids and grandkids something to remember for years to come. Marian Benton, 55, of Minden, La., purchased a Disney World getaway for herself, her husband, their two kids and one grandchild last December because "it's so rare that we get together under the same roof anymore."

Such bonding by adventure doesn't come cheap. To save money, travel agent and columnist John Frenaye suggests booking ski resorts in summer or visiting the Caribbean's ABC islands (Aruba, Bonaire or Curaçao), which are south of the hurricane belt, out of season. Or hit a lesser-known destination. Last year 's Anne Banas visited Mexico's Isla Mujeres ( ), a 30-minute ferry ride from Cancún, and fell in love with its low-key atmosphere, beachside bungalows and great snorkeling. Most rooms, even in high season, rent for less than $200 a night, and dining options range from inexpensive taco stands to three-star restaurants. She also recommends Michigan's Mackinac Island ( ). "It's got a nice summer feeling that appeals to everyone in the family," she says. "There's a town where you can rent bikes and go along the island, and lots of fudge shops." Jefferis, who took her own kids and grandkids to Grand Cayman last month, saved by renting condos (from $275 per night; ) instead of hotel rooms. The adults took turns grilling and mixing cocktails while the kids played hide-and-seek until sunset.

Several Web sites can help with planning and budgeting. specializes in group travel and can help you land special rates at hotels. If you're interested in renting a villa or condo, check and greatrentals. com , which have international listings. Ask plenty of questions (oceanfront may not mean beachfront, for instance) and get the names of previous tenants from the owner so you can check references. Also, search the name of the villa or condo complex on travel bulletin boards, like the popular "talk" section of , where seasoned jet setters compare notes on everything from sand quality to hotel cleanliness.

Next, make sure to tell everyone exactly what to expect. Knox invited Jefferis to her house for a detailed presentation. "Then, I sat the grandkids down and gave them a pep talk," she said. "I told them they had to be flexible, that they wouldn't always have their way, that some-times they wouldn't like the food." It paid off. Halfway through the trip, she asked one of her stepgrandkids, Matthew, now 23, what he thought. " 'Helga,' he said. 'It's awesome'."