Most of what I send my sims to do on dates is expansion content. If you have University Life, the bowling alley makes a good place for dates. I made a copy of the one from the university town and placed in in the bin with a few edits (like a professional bar). That’s definitely my favorite place to send my sims.
Otherwise, you could do a picnic on the beach. If you have Island Paradise send them for a romantic boat ride, or let them go jet skiing.
If you have Seasons installed the festival lots are nice for dates too. Skating, snowball fights, etc.