I have never heard of anyone's family being targeted just because they attended a gay wedding. If you love and respect the people getting married, I'd go. I highly doubt the local conservatives will be staking out the wedding and taking down names and contact information for everyone who enters the building, unless you live in a far scarier time and place than I do. Granted, I do live in Massachusetts, where gay weddings are legal ... Are they legal in your province? I don't know the Canadian law in this matter.