Among the hottest trends in travel is family travel, but multigenerational trips — which span three generations of a family — are quickly gaining popularity. Last year, 32 percent of vacationing U.S. grandparents took their grandchildren along. In a recent study, Preferred Hotel Group found that 40 percent of U.S. leisure travelers — about 21 million of them — took a multigenerational trip in the previous 12 months. The study also found that nearly eight in 10 multigenerational travelers plan “milestone vacations,” with half planning around a life event like a birthday, anniversary, reunion or wedding. There are many reasons