There is a post by Denise right above your post. Welcome Pickups seems to be the choice from what most of the folks are saying. Your situation is somewhat different in that you need a van. While I have no direct experience getting transport at the airport, i personally don't like not knowing if I have a ride or not at the last minute. I'd rather book on line ahead of time, thus knowing exactly how much it's going to cost and that the driver will be there at the appointed time with the requested vehicle. From what folks are saying, there's a lot of hanky panky that goes on among the drivers and the rates they quote, etc. If you read through the comments, even though they are several months old, you get the gist of what's going on. Did you try Suntransfers.com? They seem to have goo rates and they offer free cancellation up to 24 hours before, so if you find something better, you can always cancel. Make sure if you book that you do get a site that gives free cancellation. I got burned twice when I booked airport rides and then had to cancel. One company charged me 20% of the total cost and the other charged 20 euros on a round trip that I paid 74 euros for. Not going to make that mistake again! Anyway, I don't know if this is helpful at all, but I wish you and your family and wonderful trip.
