The being away on vacation gives you a good reason to use without mentioning the tantrum and things that have gone on. Simply saying you didn't realize just how disruptive it was to your group to have a child that came so sporadically and that it isn't fair to the children to never know what to expect at daycare or for the pt child to properly settle in since the group is used to playing together without him. For that reason you feel it would be best to terminate care effective insert date). By email you could do it even at the end of the first week of their vacation ie after you have had time to realize how much calmer it is in daycare. But give the effective date for two weeks after their return so three weeks from sending email. Even on vacation there are plenty of online sites she can look at while lounging on the beach or whatever they are doing for vacation.