MMF, I am where you may soon be in terms of your family split even more than they are already. It is not nice and personally I wouldn't recommend it to anyone.
My H promised me faithfully when S16 went to live with him that he would encourage him to still see me. That has never happened. In fact he now actively encourage S16 NOT to see me. In the last month I have seen my son for a total of about 20mins. I cannot go to see him and he chooses not to see me as his friends/girlfriends have a greater priority in his life. To be fair he is not spending an awful lot of time with H either. I'm sure that suits H as it means he has not had to alter his lifestyle with OW.
I'm not telling you this to 'poison' your mind to the idea just to warn you that sometimes the wolf might be in sheep's clothing.
Take care.
Me 43 XH 45 M 2.7.88 Divorce 7.10.09 Kids D20,S17 & D15