Encinitas is about 30 minutes north of downtown San Diego. If staying in the downtown area, southbound traffic can be heavy during rush hour. Swami's Beach is a great place to watch the sunset while waiting for traffic to die down.
San Diego has a year-round temperate climate, so families can do these outings throughout the year. If swimming in winter, there are wetsuit rentals at many of the surf shops on Highway 101.
Moonlight State Beach parking is paid parking, so look for free street parking around B Street. It would also put you closer to Handel's Ice Cream. If you sign up for the Handel's newsletter, you get a free cone if the coupon is used within 48 hrs.