I just have to say to be careful for people planning a first visit. There are a ton of YouTube videos of kids not responding well to a last minute surprise - crying about not wanting to get on a plane, "but I thought we were going to grandmas!
", etc. whatever awesome surprise - give the kids some time to process
Unless you've been before and they know the drill - then last min can be pretty awesome
Our favorite video is a local kid whose mom surprised him by driving to the park instead of school. He's CONVINCED (even after seeing the big entry gate) that she's trying to take him to the dentist <3