When I am hired to perform strolling at a wedding, all of the talking/booking is done prior to the event, months and then again days ahead of time. This day is about them not you. You are in the background entertaining guests and making sure everyone (especially the people who aren't dancing and just sitting at tables) I don't ever and don't plan on ever kissing the bride on the cheek nor have I asked for a photo op with them. However; see the last paragraph regarding photos
You have to remember that they are being pulled in a million different directions by many people and they are stressed out a bit. Performing for them (the bride and groom) should definitely wait until the dancing and music and reception has started as pictures and cocktail hour all happen prior to the meal. The bridge and groom barely have enough time to even enjoy their meal and visiting guests at tables.
BEST piece of advice so listen: MAKE FRIENDS with the PHOTOGRAPHER and give them your business card and offer to give them a free gig/bday party show for their child, niece, nephew, etc. In exchange all that you ask is for about 8 to 10 good shots of you performing at tables or for guests with you in the picture and right at the moment of astonishment where the entire table is clapping or in disbelief. Have these emailed to you with their permission, and put those suckers on your website and social media.