If it were me I and all three children were equal I would go with the youngest as they would be with you the longest. I'm not a big fan of interviewing or transitioning and I only take one before and after as they take up a space in the summer .... Right now I have one that will go to school this sept and she is staying for b/a school and then next sept (2013) I will have two more going to school so I will need to fill those spots .... If you take too many the same age they all leave at the same time .... Thats my nickel !