How do you tell the kids that the house needs to be sold because you and your spouse are getting divorced?

We have been separated for 4 months-I moved out of the home and my ex stayed. Now it has become too much for him to handle financially and we need to get divorced so we can both move on. I think in the long run it will be better for our sons (ages 13 and 11) so that they can move on emotionally as well but I know that they are going to freak out at first because they still had hope that their dad and I would work it out. They also stil seem pretty attached to that home instead of mine. Of course the fact that I haven't been able to finish decorating mine to make it cozy for them hasn't helped and I haven't been able to afford to because their dad shorts me every month on child support. I really need to get all of this settled legally but am scared to deal with my sons reactions. Can anyone give me some advice that has been in this situation?