I have recently converted my photography hobby into part time business focusing on outdoor portraits, family pictures etc. I have received an offer to shoot a wedding in November. I currently have these lenses: 50mm 1.8f, 18-55 f3.5-5.6 and 55-250 f3.5-5.6. What other lense should I purchase that will be good to shoot at the wedding. I am considering 24-70 2.8f or 16-35 2.8f. The wedding is going to be at a banquet hall (not in church). Please let me know what sort of settings should I use on the camera (i.e. AV mode, P mode etc..what about ISO, fstop, exposure). Any help or assistance is greatly appreciated.