newgirl you aren't alone is saying that they can rebuild their relationship but it is going to take time and both of their commitment. We are being realistic here. This is the third time, he's caught her sexting.
Its not like they didn't realize that something was wrong with their marriage after the first sexting incident. Jack has said that since the first incident, he has made more of an effort to do spend more time as a couple and to give her the attention that the sexting gave her. He was trying but she kept sexting away. I am sorry but its not going to work if one spouse is not making an effort.
Jack, I know this weekend will be hard for you all. Try to get through it for the sake of the kids. Make a pact to aside your anger and hurt and discussion on sexting for a few days so that it will not spoil the Christmas joy for your kids. Afterwards, try to make some concrete plans about how to go about making your marriage better and stronger.
This might not be the best idea as it will be very hurtful with some home truths but maybe write out what are the good things you like about each other/marriage and what things that you would to change in each other/marriage. From there, work out a plan for each of you. Every three months or so, sit down and review it again.
I know it sounds analytical but its a step forward.