I agree with the keeping it simple 'Johnny is moving on in his journey and wont be able to come anymore ~ we will miss him for sure'

I have not had to deal with the leaving on 'poor terms' so one of the things we do for friends missed at least for the first little while is we send them 'love notes' every few weeks about what we've been up to, color a picture for them or whatever and send it in the mail ... and as long as my current crew is 'asking' about the child we keep going but over time they tend to 'fade' as new friends replace them and either the kids here stop asking or the kid who left stops 'responding' and well than they just exit out of our lives for good.