Honest mistakes won’t ruin children. Children will be patient, supportive and forgiving and help if they know that you make mistakes, that you have weaknesses, and that you may need help.
Children need to know the truth; to be honest with them gives them a sense of security and predictability. It doesn’t matter that things will go wrong if we know that it is only that things went wrong. But you can recover; survive. Maybe not without pain or hard work, but still possible. But children do not need to know the whole truth, only the part they are ready to understand and absorb.