Promises to little kids matter most because they believe you completely.

A child has no way to discount what you say. Adults hear a promise and quietly apply a probability to it, allowing for traffic and tiredness; a small person takes it as a fact about the future and arranges the afternoon around it. When it does not happen, they do not conclude something came up, they conclude something about you.

Promise less to the little ones around you and be precise: not soon, but Saturday after lunch. If something gets in the way, tell them yourself and give them the new day.