La Jolla Mom
Don't forget your sunglasses! You'll be wearing them constantly in any season, and polarized lenses can be especially helpful for seeing around town.
Bring a hat for sightseeing and a hat for the beach for extra sun protection and to shield your eyes. Packable wide-brim hats are a popular choice in San Diego.
Bring SPF for your face, lips, and body, and remember to reapply it throughout the day.
A waterproof camera, such as a GoPro, can be great for beach photos and activities like kayaking and tide pooling. Domes can be fun accessories for getting over and underwater photos.
Consider bringing a waterproof cover for your smartphone for beach use, even if you're just hanging out on the sand. Avoid plastic or paper bags, as seagulls are known to be thieves and may grab your phone thinking it's lunch.
Many beachfront hotels will have sand toys available for kids, but you may also want to bring collapsible pails, waterproof playing cards, and other fun beach toys to keep children entertained.
An umbrella can be bulky, so you may want to consider a portable beach tent for shade at the beach.
Many beachfront hotels will provide beach chairs, but if you think you'll need them and are driving to San Diego, it may be worth bringing a few of your own.
If you're driving to San Diego, bring wetsuits for colder ocean temperatures in the winter months. Otherwise, they can be rented around town, even for kids.