Hey /p/

I'm shooting a friends wedding in March, and it will be my first wedding. I've done local concerts, headshots, and business portraits, but this one I'm most worried about as it's a "special day" and I don't want to be the cause of bad memories. Now, they are very relaxed (and technically already married, this is just a ceremony) but I don't want to fuck up.

What gear is essential? I don't have the money for a second camera body, but they are paying me relatively well and I mentioned I would rent nicer lenses (the bride is a photographer) and they would reimburse me for the rentals. I have a Sony a7, but I also have a power E-Mount to Canon adapter that I use so it opens up the ability to have a wider variety for lenses.

Right now I have semi-affordable lenses which include:
Canon 50mm Prime f/1.8
Canon 75-300 (Which I rarely use, I feel the quality really lacks as it was a sub $200 lens)
Tamron 28-75 f/2.8 (Which is the main lens I would like to replace, but I'm not sure if I should stick with a Sony lens or if there is a better zoom Canon lens)

I also have two batteries, multiple SD cards and will be renting a flash (Which I need advice on as well)

Any insight would be greatly appreciated!

Thanks

Will bump with pictures of my dog because why not.