MMF, I agree with Shew, it is a pretty delicate situation with your daughter. Could you raise the topic with her in some gentle way without immediately bringing the implied pressure to decide upon her? That way you can test her out to see if she wants to decide, and then if she does, you of course can just step back and let it happen.
but of course I also see the wisdom in delaying the who thing until later, for the sake of the boys.
and if she does elect to go to her mother's place to stay, you would probably want to talk with your daughter about your own feelings about it - telling her that you would like to still see her regularly, and maybe the two of you could make a regular date - like saturday afternoons or whatever.
At a certain age the responsibility to facilitate a relationship between the parent and child lies with the parent and child, not with the other parent. The other parent is going to do whatever... you cannot let that affect your relationship with your kid. you cannot depend on the other parent for your relationship with the kid.
