Oceanside is right near the marine's Camp Pendleton and I think the town survives from their custom. I've always thought it to be fairly safe as a result of the proximity to the Camp.
There are/were a couple of surf 'legends' that opened up stores in Oceanside; so it does attract the surfers as well.
And aside from the attractions that Peri has mentioned, the San Diego Wild Animal Park might be closer than the San Diego Zoo.
There is also the upmarket seaside town of La Jolla nearby. You might find sea lions on one of the beaches at La Jolla.
You'll be near the Mission San Luis Rey should you want to have an excursion to kill a couple of hours.
I personally like going to the town of Julian; it is an alternative to the beach. But you might already have enough to do and/or might prefer to stay nearer the seaside.
Have fun there. About the only thing that I don't like about that area is the traffic where the 5 and 78 intersect. It used to be reasonable but traffic is pretty slow around that intersection.