We made the announcement on Saturday afternoon as planned :) My sister called us on Skype, i got everyone indoors, grabbed Mum and Dad's card and hid it in my jumper, and went back to the computer. Her boyfriend was in the shower however so we waited for him to finish and come back to the computer - i asked to speak to him but didn't give a reason. My sister looked puzzled but didn't question and we all continued talking while Dad was in the kitchen preparing dinner.
Her boyfriend then got out of the shower and back to the computer, and i asked him to retrieve the envelope i'd sent my sister which he'd hidden last week when i told them it was her birthday card, telling him there was actually two cards inside - one for her birthday, and one to be opened today. But we were nearly foiled - the kitchen had gone quiet and Dad and my brother were nowhere to be seen! Eventually we checked the garage and saw the car was gone.
Plan B.... i told my sister and her boyfriend that Mum and Dad had to both watch them open the card, and could they wait 15 for Dad to get back from town? They thought this was rather intriguing but agreed to wait, and would call back when my sister had had her shower.
Dad got back a few minutes later and Mum told him we'd been waiting for him and that we were going back on Skype later. Hubby and i pretended it wasn't anything overly exciting and went back to various occupations to pass the time, then we heard the Skype ring tone. Sister and boyfriend were both sitting in front of her computer and we got Mum and Dad into the office... all ready. My sis said they'd been trying to guess what the card was for and holding it up to the light to see if anything could be seen through the envelope. She wouldn't say what their guesses were though! She asked if they could open it now - i said yes, but the reason i wanted Mum and Dad to be here before you opened it is because i have a similar card for them. Pulled it out of my jumper which they were amused at and handed it to them, and then gave the go ahead for both parties to open their envelopes :)
Mum had hers with Dad looking on, she looked at the calendar picture on the front and quickly flipped open the card, and exclaimed, "I knew it!" Sis and her boyfriend had flipped theirs at the same time and were sitting there both with big grins. I suspect that it had been one of their guesses :) There were congratulations all around, very excited family, and all were impressed with the way we'd pulled off the surprise. Def worth waiting to do it!