The thank you reply for someone else's invitation to dinner is as follows: Thank you very much for the invitation. I look forward to enjoying this delicious meal with you.

Thank you for your hospitality. I will make sure to be on time for the appointment.

Your invitation is so thoughtful and I really appreciate it and hope we have a great time.

It's a great honor to receive your invitation and I look forward to meeting you and enjoying this meal.

Thank you for thinking of me, I'm happy to accept your invitation.

Thank you for the invitation and I'm looking forward to our gathering.

Thank you for your invitation. I will arrive on time.

Thank you so much for thinking of me and I look forward to spending some quality time with you***.