Double Date etiquette?

Have any of you Jellies here done this? How does it work? Let’s say it’s not just dinner and drinks but about a whole day’s worth of sightseeing, eating, talking, and drinking (easy with the booze of course and, yes, I am back to casual drinking, if some of you were curious :)). Would it make a difference to the scenario if the other ‘couple’ were not actually dating (I have to iron out some of the details, but I still have about 2 weeks left to do so)? And, finally, if it turns out this actually is a classic double date, who pays the bill (if it’s dinner, drinks at a club, or maybe a gig at a local jazz club or some such place)? Appreciate any tips you can give me on how to, not only, survive this scenario, but also make it a fun experience for all parties involved.

I do not want to get into the details here, so general tips will suffice. Thank you! :-)