Loooove the serial killer way

Amongst all my friends I have two couples who cannot keep their hands off each other in public. Don't take me wrong, I think it's endearing to be in love and to be able to show your affection, but if you live together, seriously, must you do it all the time? Most couples I know act like "normal" people, not having to touch and kiss when with others. And I'm not referring to teenagers, I do remember what it was like. But grownups? Once ok, but like a serial killer they seem to must have to do it repeatedly. I don't find it repulsive, just unnecessary. Reason I bring this up is I'm having one of these couples for dinner tonight. Was contemplating seating them on opposite sides of the table, but I'm sure they would just toe-flirt or something instead. And yes, I like them as people, otherwise I wouldn't have invited them but I'm dreading the lovey-dovey a bit...