I'm running Granny Camp this summer. I'm going to teach my grandchildren how to row and catch crabs. How to live without television and sing around the piano. Play with their cousins. Eat apple pie. 

The grandparent visit is a ritual of summer. It's also the stuff of nostalgia. Gone from memory are the mosquitoes and scraped knees. It's all apple-pie happy time. Grannyhood is up there with Motherhood as an icon of family virtue. In the past few years, books have sprung up like wild raspberries in August: "My Granny's Purse." And "Granny Torrelli Makes Soup." And "Granny D: You're Never Too Old to Raise a Little Hell." 

What's forgotten is that this surge of hell-raising, soup-making, activist grandparents is a relatively new phenomenon. 

In 1900, life expectancy was under 50. Men and women over 65 accounted for less than 5 percent of the population. Today life expectancy is more than 75. In 20 years, people over 65 are expected to outnumber teenagers by more than two to one. 

The pyramid shape of the population with a few older people on top has given way to a rectangular shape, more like an office building, with each floor representing a 10-year age cohort. With the generations more in balance, grandparents are no longer a glorified rarity, but an entrenched sector of the family. 

That opens the way for a significant, decades-long relationship between grandparent and grandchild. Carol Bentley, 58, an English teacher in Fairfax, puts it this way: "My grandchildren think of my home as their second home. They have a room with books and art materials. . . . They sleep over often." 

There is a special warmth and wonder in this bond. Bentley remembers one morning when her 4-year-old grandson and 3-year-old granddaughter ran into the kitchen while their parents slept. "A soft rain was falling outside. We all sat in our pajamas in an old wicker chair on my deck under the umbrella, listening to the sounds of the rain and the early spring morning," she explains. A moment revealing "what a very significant part of my new life my grandchildren are," she continues. 

And what a significant role she plays in their lives. Grandparents are not only more numerous, they are also healthier than in the past. Gone are the old-fashioned images of Granny glasses, stolid black shoes and rocking chairs. Today Gramma wears backless jumpsuits, goes to aerobics, holds down a job. So does Grampa, who is starting a business, learning the tango, mentoring in a school. 

Most men and women will see their granchildren well into adulthood. That's a long opportunity to make a difference in their lives and transmit values down the family tree. 

But it's not easy. This novel role of grandparenting is not well defined. According to research by Maryland sociologist Florence Rosenberg, it can range from surrogate parenting to sending the occasional birthday card, and everything in between. How much involvement is too much? Not enough? How do you draw the line between caring and intrusion? A lot depends on your relationship with the parents because they can limit and modify the grandparents' role. Geographical distance is a huge obstacle. And if the parents divorce, the family dynamic can change dramatically -- bringing you closer to the grandchildren, or pushing you away. 

For many families, the solution to intergenerational bonding is the summer vacation. It may be renting a beach house together for a week or camping out in a national park. One scenario is the "grand exclusive" visit: the parents stay home and it's just the grandparents and grandchildren together. 

Marge and Bob Kitterman of Americus, Ga., have found a way to work and spend time with their grandchildren. When Bob retired from a banking career, they jumped in the RV to roam the country and soon joined Care-a-Vanners, a group of 1,000 people who live in motor homes and work with Habitat for Humanity to build homes for needy families. Their life combines the love of the road and freedom to explore with the commitment to "give back." 

It also allows them to take their grandchildren on trips in the RV. One year Colorado. The next year Maine. 

"It's a wonderful way of bonding," says Marge Kitterman. "It's important for Bob and me to get to know them and important for them to know what we are doing. We want them to volunteer the way we have done." 

Grandparenting is different from parenting. "We don't need to reprimand them when they talk with their mouths full," she says. What's important? Getting connected, sharing stories. A child can't be loved too much. 

The trip lasts a week. The prime age for this sort of excursion is in the 8-to-13-year range, say the Kittermans: old enough to travel without parents, but not yet off on their own tracks. 

The Kittermans give their grandchildren a lot of autonomy. For starters, it's up to them to plan the trip. The grandparents pick the region of the country and the kids plan the details by contacting the chamber of commerce or going on the Internet. 

The grandchildren are also expected to keep a journal. "We go over the trips. We don't want them to forget our beautiful country," says Marge Kitterman. 

And the kids set the rules of the day. Sometimes they have upside-down days -- breakfast at night, chicken in the morning. Stay in jammies all day. Play cards at midnight. "Go for it. Whatever you want to do, we'll do," she continues. 

For the Kittermans, the trips are about love and legacy. They get to play with their grandchildren and make a mark on a future generation. The summer sojourn with the "grands" is a short, intense love affair across generations -- the stuff of memory and meaning for both sides of the age divide for the rest of time. 

It can also be exhausting. I met a couple taking a leisurely coastal bus ride in Portland, Maine. As the man explained: "We've just had the grandchildren for two weeks and now we're taking our vacation."