I would lean towards postponing here. Traumatic loss of a young teenager is devastating for a family, like a great big psychological bomb going off. They don't need to be trying pull themselves together to face a wedding in the same week as the funeral. Really. For starters they will be absolutely exhausted and battered physically, never mind emotionally.
Is there someone on the near periphery of the loss that you could run this by? If you do postpone, make sure you are clear that it's done as a consideration for them, not so that's you can have your full moment of glory untainted by death.
If you do go ahead, I would make sure that people know that it's ok for them to choose no to attend without having to worry about offending you, even at the last minute.
We missed a family wedding after a traumatic bereavement, and no one gave us a hard time about it, for which I am very grateful. The timing wasn't nearly so close, but we still couldn't face it. My mum, on the other hand, went t the wedding and did a proper hijack to make it about her and her loss as much as she could. Not nice behaviour to have going on at a wedding, and very difficult to deal with tactfully.