1st wedding

[follysurfer18]

hey, i'm new to the forum and have a question. A good friend asked me to do her wedding photos. This will be my first one and it's indoors at a mill that's been converted. I currently have a sony a300 w/kit 18-70mm f3.5/5.6, sigma 70-300mm f5.6, a sony DT 50mm f1.8, and a sony HVLF-42AM flash. I will be getting a sony a580 as well. My question is would a sigma 28-105mm f2.8-4 or a tamron AF 28-105 f4-5.6 be another good lens to get? And which of the two is better as far as quality? And if not those, what would be a good one to look for w/o breaking the bank.