Well, one time my sim got invited to go out on a date. The game ended up sending her to Magnolia Promenade. At the time I had one residential home there, also another one of my families I was rotational playing, and this family had a newborn baby. While there I got a pop up warning me that if the baby's needs were not met it would be taken away. So my sim ended up spending her whole date taking care of someone else's child, and she did not even know this family. All my other dates had issues with a third wheel sticking their noses in, thus why all my sims now have their dates at home.
While at home, what I have my sims do on their date will depend on how well they know each other. But most dates will have a meal, prepared beforehand. Dance to music, and or watch a movie. Have deep conversations, tell funny stories, and jokes, with a bit of flirting here and there. Now if they are more romantically involved, then the dates will be more romantically involved included with the above-mentioned things.