Hotel Trend: Leave the Kids at Home

There's a reason for that. Starting this year, not just the pool but the hotel itself was declared off-limits for the underage set. In fact, the entire resort has been split in two, with its pools, beaches and rooms divvied up between families and child-free adults like so many slices of pie. The adults come out of the deal with the glitzy Marina Hotel, its fitness room, the spa and even Flamingo Beach, part of the hotel's private island. Families, on the other hand, get the more low-profile Renaissance Ocean Suites, where perks like the Marina's infinity pool and martini menu have been replaced by swing sets and barbecue buffets.

You don't have to go to Aruba to find this latest travel trend. In a stunning reversal of the family-friendly travel movement, hotels are starting to take the opposite approach when it comes to children: banning them. While few have gone as far as the Renaissance, hotels from Rancho Las Palmas Resort & Spa in Rancho Mirage, Calif., to Vermont's Topnotch Resort & Spa are adding adults-only amenities. Even Atlantis, Bahamian granddaddy of the family-friendly movement, is adding a sleek new adult-oriented hotel, complete with kid-free pool and bar areas. Visitors to Cambridge Beaches in Bermuda, meanwhile, are welcome to bring kids under five — provided they have a full-time nanny in tow.

What's more, hotels that have had age restrictions all along are tightening them up. At Little Palm Island Resort and Spa in the Florida Keys, the legal age has been bumped from 12 to 16. At Madrona Manor in Healdsburg, Calif., kids got a trial run when the resort opened, but now the place has just three hard-and-fast rules, says General Manager Joseph Hadley: No smoking, no pets and no kids under 12. Even rich and famous parents can't catch a break. When Gwyneth Paltrow asked if she could bring her daughter, Apple, to the 16-and-over Paraiso De La Bonita in Puerto Morelos, Mexico, she was told yes — but only if she wanted to reserve the entire property for about $90,000 a night.

Hotels say the kid-free crusade simply makes sense because adults-only trips now make up nearly 70% of leisure travel while once-hot family travel is cooling. Demographics play a role here: Boomers, who spend $157 billion a year vacationing, are getting older, and as their children start families of their own, they're back to traveling à deux. It's easier logistically, too, since hotels don't have to worry about maintaining pricey kids' clubs. Of course, money is the real issue. After all, kids don't run up the big bills that keep hotels in the black; they eat less, they share rooms, and they certainly don't order $15 martinis and $200 rubdowns.

Hotels say they're getting a great response to the movement, but not all travelers are embracing it. With all the focus on adding sophisticated perks for the kid-free set, some moms and dads are starting to feel as if they've been banished to the vacation version of Romper Room. And families with teenagers feel trapped in the middle, with children too old for the kiddie pool but too young for the bar scene. Even the hotels themselves are facing a slew of unexpected problems, everything from how to enforce age limitations without offending guests to keeping families from feeling like second-class citizens.

Catering to kids was once one of the hottest trends in travel. It all started with Mickey, of course, with the success of Disney vacations giving rise to megaresorts like Atlantis and Beaches Resorts, which wowed children with towering waterslides and jungle gyms while offering parents a stress-free vacation. Luxury hotels joined in too, with the Four Seasons rolling out a "teen concierge" and The Ritz-Carlton in Naples, Fla., launching its "V.I.K.," or Very Important Kid, program, complete with a miniature check-in desk.