It is better to be honest and have children deal with small disappointments than to lie so that later the disappointment is much greater and that the relationship with your children is damaged in the long term. Trust is the foundation of any good relationship, especially when it comes to parents and children. For example, if your child is not doing something right and you lie to him so as not to hurt his feelings, you are creating a long-term problem.
These are what are known as 'white lies' that create mistrust over time as the child will figure things out and realize that you are lying. Lies have very short legs, and if your child discovers that you have lied even if it was a 'white lie'then trust will have been damaged.
Children need to learn from you that the truth should be told. Trust is the most important foundation of the parent-child relationship, so don't hurt it when you can be honest and sincere at all times.
Being honest is always the best. You will be giving your child credibility with your honesty and even when you have to admit a mistake you have made. Telling the truth does not put you in any position of vulnerability, quite the contrary. Telling the truth is brave and your child will learn that telling the truth and being honest is what you should always do.
The reality is that children can deal with almost any disappointment if they are supported by their parents. It also works in reverse, so if parents repeatedly lie to children, they begin to doubt and mistrust even the simplest of realities, and worst of all, children will also become lying people. Honesty will always be the best teaching for your children.