I agree - be there to support her but wait for her to break free permanently before progressing into any kind of relationsihp with her.

Are the kids his? If so, could be really nasty because he'll want to be around them. If not, then it may be ok once he's out of the picture. Seems like you will have to deal with her baggage. If you two have matching-luggage, things would work out ok. But look at whether you're trying to "help" her or really feel you're compatible. Helping her goes away once he is out of the picture. Then the real work starts in making a relationship work with her and you "in the real world".