I think it’s a great idea if you know the people you are surprising would love the idea too. My husband & I did that to my mom and stepdad. She had been asking me to go on a cruise with her so I knew she would love it. I did make sure she wasn’t in the Haven as she normally is and through sleuthing I found out their cabin number….not through the cruise line. We normally talk by phone before she leaves port so I just called her and casually asked what she was doing. I found her and was she surprised. It’s honestly the best feeling in the world to plan a secret surprise and have it play out. They had a spa balcony so they hung out in the spa and we met up for lunch and dinner and shows. It worked out perfectly and I would absolutely do it again!