Communion

It would be most appropriate to have just you and your fiance partake.

If you're marrying in a church, they will have specific rules on how communion is distributed anyway.

I've seen both happen, and it's meaningful both ways. I'll be honest it's not a typical thing, so I was a bit weirded out the first time I saw it even though I grew up in a Baptist church and partake in communion regularly still. I feel like having the guests partake as well just adds a lot to the ceremony and would only consider it if you are having a small, intimate ceremony. If I'd choose a non-wedding Christian ritual to include in my ceremony I'd pick communion over feet washing.