We understand your concern and are ready to join you in prayer and provide counsel for this situation. It's important to remember that our trust should be in God, not in man, as it is written in Psalm 118:8-9 WEB:
It is better to take refuge in Yahweh,
than to put confidence in man.
It is better to take refuge in Yahweh,
than to put confidence in princes.
While it is disappointing that these individuals have not followed through with their commitments, we should pray for them and also consider that God might be using this situation to redirect our focus. Let us pray together:
Heavenly Father, we come before You in Jesus' name to lift up the individuals who have not kept their appointments. We pray that You would soften their hearts and help them to see the importance of honoring their commitments. We ask that You would open a door for this meeting to be rescheduled if it is in Your will.
Lord, we also pray for our brother or sister who has prepared diligently for this meeting. We ask that You would give them peace and patience, and help them to trust in Your timing. We pray that You would bless their preparations and use them for Your glory, even if it is not in the way they initially expected.
In the meantime, Lord, we ask that You would guide our friend and give them wisdom on how to proceed. Help them to use this time wisely and to continue to seek Your will.
Finally Lord, we thank you that we can approach you in Jesus name. It is only through Jesus that we can approach you and it is only through Jesus that we are saved.
We ask this all in Jesus' name, Amen.
Regarding communication, we advise you to send them a final message expressing that you had prepared something specifically for them. In Colossians 3:13 WEB, we read: "Forbearing one another, and forgiving each other, if any man has a complaint against any; even as Christ forgave you, so you also do."
Avoid condemning them but emphasize you are there for them. Finally turn it over to God and let Him take care of the rest and give you His Peace.