Since V-day is comming up(By the way I was just asking,I don’t celebrate it)I wondered what L&S,R&F,and
Mr.andMrs.The King did for Valintines Day(Last year and what their problay going to do this year). 
Heheh – that’s an
interesting question.
I assume that you are referring to the characters themselves, and in the world
of cars. Well, in that case:
Lightning and Sally - Took a drive up to
“Radiator Peaks”*/waterfall for a night out; sent each other valentines and chocolate.
Ramone and Flo - Spent a day/night at some local cafe’ (besides Flo’s);
went cruising along the smooth, black road of Radiator Springs – low and slow…
[b]Mr. and
Mrs. “The King”[/b] - Took a break from the track and went out to dinner; exchanged
gifts/valentines.
I’m not sure what cars would substitute for chocolate, however.
Candy-/chocolate-flavored nuts and bolts, perhaps? 
*This is what my sister and I call the scenic drive
that Sally took Lightning to in the film.
Chocolates, flowers, and a sight see is my answer for all
three.