I mix and match several different locations and activities, depending on the traits and interests of the Sims involved or whatever sounds like fun. I tend to prefer outdoor date activities in general, and opt for indoor activities at night or when there’s bad weather. I also personalize my lots to have a variety of activities to choose from wherever they go.
Some options I’ve used (which will depend on the EP or Store content you have):
Visit rabbitholes (tours, woohoo, greeting card photos)
Eat out at bistro, diner or non-rabbithole restaurant, or have a picnic
Theater (watch movie)
Stadium (attend game or concert)
Parks
Beaches
Pool lot
Dates at home
Nectary
Hangouts
Bars/clubs/lounges
Simfests at performance venues
Festival grounds
Bowling alleys and arcades
Resort stays, diving, or other water activities like waterskiing or windsurfing
Store activities (gondola rides, roller coaster, circus, casino, Ren faire, etc.)
Use NRaas Traveler mod to take an extended “date” vacation in another world