Splitting custody is tough, and not just for the children. It can also be hard on the parents. How much communication should happen with the parent who doesn't have custody?
For instance, perhaps you and your ex have an every-other-week schedule. On the weeks that the children live with you, should your children call your ex? Should your ex call them? Is this communication helpful?
The choice is up to every parent. Some want daily communication, FaceTime sessions and picture updates. Others do not. There's no right or wrong answer.
Some parents have said that talking to the children when they're apart doesn't help. It just makes them miss their kids more. Others, though, miss the children all the time. Getting a call, a picture text helps to alleviate this and makes it less difficult.
One thing to consider is the potential for parental alienation. This happens when kids feel distant from one parent and close with the other. Sometimes it is done intentionally. It can cut off the relationship that one parent has with their children, regardless of custody rights.
If you're worried about parental alienation, more frequent communication could be the key to avoiding it. The more contact the children have with both parents, the closer they become. That type of closeness, coupled with an involved relationship, is the best for both the children and their parents.
Decisions like this are really ones that you have to make on your own, depending on your situation. Just make sure you know what legal rights you have as you sort it all out.