Considering the judgemental types here on the DIS its not really all that possible to not offend someone some of the time, so if you are going to find someting to be offended by, whether its the charity of choice that a donation was made (again,
not even in your name so why would you care

) or the bridesmaids wearing the wrong color for the season, decline the invite and stay home.
If you are the kind of guest who doesn't see the invite, the nice dinner, the dessert or the night of entertainment you get as the bride and groom as being a good host and hostess for letting you share their day with them, I imagine you arent the type they invited by choice
ETA I'm not saying that the bride and groom shouldn't take their guests into account with what they do, however they shouldn't put whats important to their wedding day aside for their guests. If donating to a charity is important to the bride because it has touched her family (like the OP) then I don't see a problem with possibly offending someone by it. YOu can't please everyone and for goodness sakes I think people have the right to not worry about pleasing everyone on their wedding day.