By Andrea Petersen, The Wall Street Journal

Rosewood Hotels & Resorts has a rule in its spas: Use "our 'spa' voice," says Marcie Lieberman, Rosewood's senior director of operations.It applies to all the children who come for services including the "Lily Complexion Perfecting Facial" (For ages 9 to 13. Price tag: $60) and the mani-pedi for kids as young as five (Price: $75).

Luxury hotels are boosting efforts to cater to their littlest guests. Hotels say they are responding to increasing demand for kid-friendly services from travelers, who are bringing their wee ones to high-price hotels in never-before seen numbers. The rise of later-in-life childbearing—when more couples have the money to travel—is playing a role. So are baby boomers who organize, and often pay for, trips with children and grandchildren.

"Getting to the hearts of kids is the most powerful way to get to the hearts of parents," said Mark Novota, managing partner of the Wequassett Resort and Golf Club, a 120-room resort in Chatham, Mass., that opened a new children's center in 2009. The new efforts go far beyond coloring books at check-in and teddy bears at turndown.