My DW and I managed to keep our first visit a secret from the kids. We told then we were going to stay in a friends caravan for a week but had to drop thier grandparents of at the airport on the way!
We loaded the car the night before to hide the large suitcases, and drove to the grandparents house first thing in the morning. Picked up the old guys (with no cases, we told the kids they had been sent on ahead) and drove to the airport.
When we reached the airport we asked the kids if they wanted to wave off the plane, which luckly they did. It was only when we reached the check in that we sprang the surprise!! I video'd the whole thing. It was brilliant! We still watch it 5 years later.
If you think you can do it, give it a go. Nothing ventured, nothing gained!:animwink: