NEW YORK — Christine Louise Hohlbaum and her husband took their children to Venice when they were 2 and 4 years old. Looking back, she wishes she'd waited until they were a little older.

"It was expensive, they were cranky and we said next time we'd go without them," said Hohlbaum, who lives in Germany and blogs about life as an American stay-at-home mom abroad at diaryofamother.blogs.com.

Despite — or maybe because of — the hassles, businesses that cater to families traveling abroad are booming. A 2006 survey of AAA Travel professionals found that 42 percent were booking more international trips for parents with children under 18. A company launched in 2003 called Ciao Bambino customizes upscale family trips to France and Italy and is an online resource for family travel planning. And Disney's family focused tours, Adventures by Disney, went from two European itineraries last year to eight this year.

Overall, 8 percent of U.S. outbound passengers consists of adults flying with children, according to the U.S. Department of Commerce's Office of Travel and Tourism Industries. But there is serious debate among parents about what age is the right age for children to start traveling internationally.

Maureen Wheeler, co-founder of the Lonely Planet guidebook company, recommends waiting until kids are 3, "when they're out of diapers, when they can eat food, when they can talk." If you're planning once-in-a-lifetime trips, "then maybe you don't start traveling with your children until the age of 7 to 10."

She added: "I started traveling with my children when they were babies and that's just stupid. It was exhausting."

But Wheeler said that even if her children Tashi and Kieran — who are now adults — don't remember their first trek to Nepal, they got something else out of their early travels. "I honestly think that it gave them an attitude for life, because they learned to be very flexible," she said.

Pauline Frommer, the travel guidebook writer and daughter of Arthur Frommer, started traveling with her parents when she was just a few months old. She said her father thinks international travel is wasted on small children because they don't remember much, but she's not so sure.

"Everywhere I go in Europe, I have this sense of deja vu," she said. "Beyond having a strong sense of deja vu, I have many strong memories from my travels."

Continuing the family tradition, she's taken her young daughters to the Dominican Republic, the Czech Republic, Italy, Ireland, Costa Rica and Brazil. This summer, her older daughter will accompany her to China, then the whole family is going to Scotland and Wales.