Thankfully I haven't had to move yet, but I do have a daughter your son's age (and 3 others). I think I would ask the kids how they would want to stay in touch with the people left behind. Would they like to try video email, writing letters with pictures included, maybe some supervised time on facebook with the other family or using other social media? Also talking about how they would like their new rooms arranged. Giving choices should help take some of the anxiety and replace it with some ownership or control of the situation that feels powerless at the time.
