If you have a family wedding where you have to be discrete, arrange a 'private session' for anyone kink friendly either on the same day (book a seperate hotel suite) or on a different day where you perform some form of BDSM ritual - a formal collaring. Having been to several weddings, I don't think anyone will notice, once the party starts, if the bride, groom and several guests disappear off for an hour. They'll assume the bride and groom are having sex and won't care about the other guests (drunk in a ditch somewhere? ).

If you are into voyeurism, you could have a proper formal, old fashioned European Royal wedding ceremony... after the wedding, the bride, groom and a selection of guests go to the bridal suite to watch the couple consumate the union. The groom presenting the bloodied sheets to demonstrate that she was indeed a virgin is optional... its all about ensuring the royal succession and preventing a situation where either party can claim divorce due to non-consummation (about the only reason you could give at the time).

There is a lot of pagan imagry in marriage which could be exploited - the white is supposed to represent the sacrificial virgin, red symbolises a vagina and so on.

A collar or choker to match the dress?

Walking down the ailse with some BDSM device attached - nipple clamps, vibrators, tight corsetry. Something discrete and hidden.