Sorcha and Kat have the right idea, Aine. I would only reinforce the importance of making sure they don't escape outside for at least a week, and then have a plan for what you will do if they do. If you are moving across town it is not unlikely that one of your cats might re-appear in its old neighborhood and if one does disappear, consider alerting some of your former neighbors or whoever has taken over where you lived. We've been on the reverse end of "who's cat is this?" after someone in the neighborhood has left, or recently moved in. There seems to be a sign on our porch, visible only to cats, that we will provide foster care; our own cats sometimes disagree vehemently! Good luck on your move.