Kim - I'm going to ask you to consider doing something REALLY hard. And that is - to keep this information to yourself until after Xmas.
My ex decided to leave right about this time of year. I had to convince him to stay through the holidays, so that the kids wouldn't always associate Xmas with their parents splitting up. We waited until the third week of January to tell them he was leaving.
Let your kids have this Xmas uninterrupted. I know it makes it extra hard on you (think about all the great weight loss though from the LBS diet!). But really - one more month may make all the difference to your kids' future holidays.
