Oh, another option a friend told me about....she opted to go to the wedding and not the reception. Her sister went to the wedding, stayed for an hour for dinner and a few of the early things (first dance, cake, etc) and then left. There's no requirement on how long you have to stay at a reception.
A woman whose in my mothers bereavement group decided a wedding was too much on her daughter's death anniversary and asked the couple if she could host the gift opening at her house the next morning with coffee and breakfast. She had her husband and son go to the reception hall and gather up the gifts and bring them back and the next morning the couple came and she had gotten a breakfast casserole you toss into the oven, some muffins and bagels, and she hosted the opening of their gifts. Everyone really appreciated that gesture.
Lots of ways to handle things...depends on what you feel--but honor your feelings.