Thanks to all for the suggestions, some really good ideas in this thread.
X2B and I got some way through the process last night, thanks to a bottle of wine and lots of chocolate. She did a stirling job of holding it together but I was very emotional. Understandable I guess.
We need to talk more about some of the fine details but we've decided to tell our daughter a week earlier than we had planned and then for me to stay in the house for that week, try to show her that life goes on and all that.
There are some other things as well but once we've got them ironed out and we've told the small person I'll post up what we did, what worked and what didn't.
Thanks again for the comments, I, sorry, we really appreciate it a lot.