Is it wrong to turn down an offer to be my friend's wedding photographer?

I'm an amateur photographer, I typically do street photography/photography of buildings etc.

My friend knows this and was struggling to find a photographer for his wedding, so he asked me.

I would love to do this and it would be great to say I've experienced photographing a wedding, but it's not the sort of photography I do at all. I don't know how to direct a group of people to make them look photogenic, I would feel awkward asking my friend and his future wife to pose for photos.

I feel like if I mess this up then it would damage our friendship.

I also don't have the right equipment for a wedding so I would have to fork out some money to upgrade my kit.

I need your opinions, what should I do here, and how should I communicate it to my friend?
Is it wrong to turn down an offer to be my friends wedding photographer?
Is it wrong to turn down an offer to be my friend's wedding photographer?
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