The best thing you can do in this situation is to be honest.
Assure that you were excited about the evening, and if you choose to be disappointed; be sure to be reasonable.
A few centuries ago, dating was sometimes described as a "courtship ritual where young women entertained gentleman callers, usually in the home, under the watchful eye of a chaperone," but increasingly, in many Western countries, it became a self-initiated activity with two young people going out as a couple in public together.
Before dating a man with a child, you should know that they are very concerned and choosy about their dating options.
They usually avoid getting into serious relationships and do not easily accept new partners.
They use their time wisely, and if he is a good father; he will want to spend lots of time with his children.
Thus, the reason for avoiding serious relationships.