Make it set in stone that you call the kids every day at a set time. Every day. Your exw can do the same thing when they are with you on your weekends. Even if it is for a quick "I love you," that door stays open. They realize how important you are in their lives and vice-versa. We do this at/around 7pm. It is something that my ex instilled. Now, there are a some times when the kids are busy, etc., and would rather not have to drop what they are doing (and ex should just say a quick Hi and hang up), but I think my youngest especially looks forward and counts on this contact with him.
