By Michelle Tauber Sharon Cotliar
December 13, 2010 12:00 PM

Ask any parent: A vacation with the kids at Orlando’s massive theme parks is a thoroughly exhausting endeavor. But Michael Douglas returned from a Thanksgiving getaway with wife Catherine Zeta-Jones and kids Dylan, 10, and Carys, 7, looking tanned, well-rested and brimming with renewed vigor. Attending a bris for the newborn son of close friend Ronald Perelman in New York City on Nov. 28, “he was full of energy,” says Perelman. “His spirits were high.” He and Zeta-Jones were among the last guests to leave-but not before Douglas made plans to hit the links with a golfing buddy. Says Perelman: “He’s rocking and rolling.” Douglas himself is a bit more circumspect. “I feel stronger every day,” he tells PEOPLE. “But it’s a long road back.”

It has been a long, hard journey for the 66-year-old Oscar winner, who finished a grueling eight-week treatment for stage 4 throat cancer in early October after doctors discovered a walnut-sized tumor on the base of his tongue. In the weeks immediately following radiation and chemotherapy, Douglas-who never needed a feeding tube but relied on a primarily liquid diet due to problems swallowing-lost roughly 20 lbs. and battled fatigue. “The first four weeks after treatment were hell,” says a source close to the actor. “That was the worst part.” Now, as he slowly regains his strength, Douglas must wait until January before doctors can determine whether his cancer has been successfully eradicated (see box). In the meantime, Douglas is cautiously optimistic. “We are very happy and thankful with the way things are going,” he says, noting that the Orlando vacation was an opportunity to express his gratitude to his kids. “Dylan and Carys have been so amazing throughout all of this,” he says. “Catherine and I wanted to thank them the best way we could.”

Visiting the Wizarding World of Harry Potter at Universal Orlando on Nov. 27, the kids “were hyper-excited,” says an observer. At one point the family indulged in the park’s signature butterbeer and compared foam mustaches. “Michael had the best of the bunch,” says the observer. “They were all laughing.” Three days earlier at Walt Disney World, Douglas and Zeta-Jones, 41, hit plenty of rides and were spotted tenderly holding hands while the kids took in a Christmas-lights display.

Those close to them say the ordeal has further united the pair, who celebrated their 10-year wedding anniversary last month with a romantic spa getaway. (Contrary to some reports, they did not renew their vows.) “Their marriage is solid as a rock,” says a friend of the couple’s. Zeta-Jones, adds the friend, “is a strong woman and very practical. There’s no two ways about it-that’s the Welsh in her. Neither one of them are people who would wallow; they just deal with what has to be done.”

Even at his weakest, Douglas-a “spiritual” man, according to his friend Perelman-was determined to stick to his routine, often walking hand-in-hand with Carys on her way to school near the family’s Upper West Side home. (He has also visited his oldest son, Cameron, 32, in the Pennsylvania prison where he’s serving time on drug charges.) On weekends the clan often retreat to their home in Westchester, N.Y. “These things can either tear families apart or make them stronger,” says their friend. “This has definitely made them even stronger.”

Looking ahead, Douglas-who’s returned to eating solid food and is practicing yoga-plans to promote Solitary Man and Wall Street: Money Never Sleeps during Oscar season. He’ll also begin taking piano and voice lessons for his role as Liberace in a biopic scheduled to start shooting in 2011. Most important, of course, Douglas hopes to get a clean bill of health in the new year. “There’s still some uncertainty, but he’s definitely feeling so much better,” says the couple’s friend. Adds Perelman: “He’s dealt with it. Now he’s ready to move on.”