Any suggestions for the newly divorced

I was the one who left my ex, so I cant really relate to your daughter, but from my opinion, I would suggest to her to take this time and get to know herself again, do all the things she wants to do before she jumps back into another relationship. Dont go running to another man to make her feel better, she needs to heal before she starts dating again.

does she know why he left her? was it another woman?

I'm sorry this has happened to your daughter, make sure you are there for her, right now is when she needs you and all her g/griends the most.
and then her son, he may feel it's his fault, he really is going to need a lot of his family there for him right now.