VIP guests receive many invitations. A generic invitation with their name in it doesn't stand out. A personal message explaining why their presence is specifically valuable does.
Send the invitation personally where possible. Call them, or have a known contact send a direct message. Follow up with a formal confirmation. A week before the event, send a personal message. Include practical information and a specific reason to look forward to the day.
After the event: send a personal thank-you within 24 hours. Reference something specific from the day: a conversation, a moment, a next step. That closes the loop on a good VIP experience.