+1 for Mark.
Denise this is again becoming too complicated. On camera flash will be plenty good enough for your first wedding, it will work everytime.
It is all well and good to appreciate all the well intended advice from people that have shot 1 wedding to people that have shot 1000 weddings. But this is your first wedding and your client wanted you, because she has an idea that you are the best fit for her. You don't need to change. You don't need to be overwhelmed for your first wedding. Just be prepared, use what you have and be yourself, that is what your client will want.
Go and watch a wedding in the park, you will be surprised how simple it looks. You have the gear(one extra body will be a sensible backup), you have the skills, that will create the confidence and then all you need is the personality. We know you have that and obviously your client thinks that already.
You can do this, easy.

I hope your bride doesn't read this forum, LOL.