Honeymoon

So we head off to our honeymoon in the morning, we have a week without the kids. We're planning to do anal for the first time, hopefully check out a swingers club, and definitely have group sex. He wants to see me be filled airtight and i love the feeling of being full so thats what we're hoping to achieve.

Question is, and yes ive done some research on it, but he's very well endowed so i'm a little scared for the anal part. How can i prep so it doesn't hurt? And whats the deal with gaping? How do i clean out before that to avoid a very unsexy mess?