Question:
I've been asked to participate in a religious wedding should I go?
Answer:
If this is simply a question of invitation to attend a wedding ceremony which will happen to be religious, there isn't much reason why you shouldn't go. The mere fact that the ceremony is religious shouldn't dissuade you unless the ceremonies are so long that you might fall asleep or are such that you can't avoid some level of participation which bothers you. Some religious rituals really are extreme and you may not want to be around them.
The purpose of attending a wedding should not, however, be for you to watch religious rituals (and so you shouldn't treat it as such). You should be there to demonstrate support and love for those who are getting married, not the religion they happen to follow. Your personal beliefs should not interfere with your love and respect for them, at least so long as their personal beliefs are not being imposed upon you.
Refusing to attend the wedding, however, sends just the opposite signal: it tells people that you don't consider them as important as your rejection of religion. Others will necessarily perceive this as a rejection and a personal rejection at that. Perhaps these people really aren't important to you; but if they are important then you need to take care that you don't communicate such a message to them inadvertently.
When it comes to participating in religious ceremonies, however, the choice becomes more difficult. This is something which must be addressed on an individual basis because your answer will really depend upon your convictions and upon the nature of the religious rituals themselves. However, it is probably a good idea to accept such invitations to participate and to do so with respect except when it will compromise your personal convictions.
There is certainly nothing about participating in a basic wedding ceremony which should compromise the convictions of most atheists. Even when the ceremony is very religious, there are few instances where you are likely to be expected to have any active role in the religious aspects those are normally reserved for the bride and groom.
The one case where you might be expected to do something is if you are asked to give a religious reading during the ceremony. Not every wedding includes readings, but many do and many of those tend to have a religious theme. If people know you are an atheist then it would be very strange for anyone to ask you to read a religious text you'll just have to gently remind them that you would feel uncomfortable doing that and offer to help out in some other capacity.
If they don't know that you are an atheist, then perhaps they are assuming that you are part of the same religion you used to be; in that case, you have a more difficult problem before you. It may not be possible to decline gracefully without giving a good reason because such a refusal may be interpreted as a personal rejection. On the other hand, you may not be prepared to "come out of the closet" just yet and in these circumstances.
Outside of such situations, you will probably spend most of your time at a wedding ceremony watching quietly while everyone else has to remember where to stand and what to say. You don't need to sing hymns with others. You don't need to kneel when others pray. You don't even have to stand when others stand you can just remain seated where you are. All you really need to do is be quiet and show some respect for others. Then, once the religious portions of the ceremony are past, you can have fun with everyone else.
Dance, eat, talk, drink, meet new people, and enjoy a series of experiences which don't come along every day. There is so much more to a typical wedding than religion anyway, why would you want to miss out on it if all that is required is a bit of quiet sitting? Everyone else is happy and having fun, so don't just sit at home.

