Dear Ms. Smith,
I am sending this letter to convey my deepest gratitude for the invitation you sent me for your wedding. I am so happy for the wonderful experience this event is sure to bring you and your husband to be.
I am accepting your wedding invitation and I feel so honored that I am invited to be among your list of guests. I understand that guests have to be dressed appropriately to fit your wedding theme. I will prepare for the occasion earnestly so you will not be embarrassed for my presence.
I am sending this letter with my sincerest wishes for you and your future family. I hope you find the courage and the endeavor to build a strong foundation in raising your children as your good parents have raised you. Good luck to you both.
God bless and hope to see you soon.