Dear …
What a __(wonderful/great/fantastic/etc.)__ birthday party __(you planned for me/that was/etc.)__! Thank you so much! I was really surprised by it all and absolutely delighted with all those who came to celebrate my __(#)__ birthday with me. You can’t know how much that meant to me.
And to see how much my family cares for me to pull this off…how do I express the thanks and gratitude I feel towards each and every one of you? I wonder if you really know how much joy you bring to me and how truly fortunate I am to have you in my life. You are the fuel to my happiness and success.
You know, a birthday is really nothing more than just another day without the people you love to share it with. And so, I thank you for making my birthday so special by being part of it. __(It was such a/Though it was a milestone birthday, it was more the)__ memorable day because of everyone who was there to help me celebrate it! Again, thank you! I love you all!
Yours always,