Congrats Mom2of2! And good luck keeping the secret from them!!
In 1999, I was graduating from seminary and my little sister was graduating from college, so Mom and Daddy planned a surprise vacation for us. They'd told us to hold the dates, but we both figured we were going to the beach since the timing matched up with when we usually went. Well, at Thanksgving Dinner, Daddy went into their bedroom and came out with 2 shoe boxes all wrapped up. Mom looked at him with "the look" and said, "I thought we were going to wait until at least Christmas." Daddy's response was that *he* couldn't wait any longer.
So we opened the boxes and each found a Disney character picture frame ~ the kind where the characters are holding the frame part that slides in and out of their hands as they peek around it ~ with a little piece of paper where the picture goes saying "We're looking forward to seeing *YOU* with your family at the Caribbean Beach Resort May 26-30." (My sister got Mickey characters and I got Pooh characters ~ reflecting our personal faves...I love Mickey to death, but I've always been a Pooh girl at heart.) It was really cool ~ so that's one possible suggestion of how to tell them when you're ready! Others may have other ideas. Incidentally,those frames now hold copied of the picture Mom took of us sitting at the Partner's Statue in front of the Castle from that trip!
Have an awesome Disney Day!!
~Beth