Please someone help me correct my grammar for my Apology Letter,.

Hello, could someone please help me correct my grammar in my letter,. We were invited to an event as an exhibitor/merchandiser, we were grateful for the invitation but due to our merchandise that we ordered were delayed.. So I want to write an apology letter for a organizer that we can't participate. I'm really not confidence in my English, so hope you could understand what i want to express. I will be really grateful if you could help me.

Here's what I want to write:

Dear Sir:

We would like to express our sincerest apology that we can't participate as an exhibitor in the event. We deeply apologize for the inconvenience that we can't be part in event due to our lack of supplies and preparation.

We were just a small establishment that sells merchandises such as official albums and fan goods through online webshop. And we were really looking forward to be able to experience this big event. But unfortunately the cargo that we were expected to arrive from our supplier was delayed. We contacted the courier company and they said that it will take a few days to track the cargo. We were really worried and anxious that the package will not to be able arrive in time. The merchandises that we ordered areWe really didn't expect this incident to happen. We sincerely apologize for the inconvenience.

We really don't want to cause you trouble and we deeply regret not be able to participate in this big event. We do hope you could accept our apology and we also hope we could make up for our mistake. We do pray for your consideration in this regard.

Sincerely yours,
Our group

I really want to express my feelings and sincerest thoughts in this letter. I regret that I can't participate because it is a big production

PS. I'm really sorry for my horrible English. Please help me. I will wait for your response. Thank you very much,.