I found myself in a very similar situation last year... though we don't have kids, my husband admitted to being in love with another woman, and eventually left me for her. He then changed his mind, and came back to me, and agreed not to see her while we re-built our relationship with different boundaries. She didn't wait for him, but we are happy in a newly poly relationship.
It was a very challenging thing for me, to change my thinking from being extremely monogamous. I think it was a great idea to join this board: I wish I had had the courage to do so in my investigations of what it means to be poly. I borrowed some books from friends, interviewed them, and observed their relationships for a period of about six months. What I found most helpful was a book written memoir-style about the journey of a woman's journey towards polyamoury, how she cheated on her husband, confessed to him & worked through it, and their path to solid and comfortable boundaries together. I appreciated being able to see the whole process, and to begin to understand her feelings, which were similar to those of my husband, without all of the personal pain that accompanied them. It's called "Open: Love, Sex and Life in an Open Marriage" by Jenny Block.
I also liked Tristan Taormino's "Opening Up", though I wasn't ready to read it until I had grieved for a while.
I'd be happy to share how things went between my husband and I, if you have any questions, or if you need to let off steam or anything, PM me...