Places to stay and go. From SanDiego to LaJolla and SantaMonica.

Budget? What sorts of things do you enjoy? How many days?

5-6 days. Whale watching aircraft carrier Queen Mary zoo 4star hotels

Okay. What do you want to know? Do you want us to plan your trip for you?

>>Places to stay and go.

Santa Monica is not in San Diego, it is in LA County, two counties north of San Diego, or about a 2-3 hour drive each way so not a day trip.
Or are you maybe looking to split your stay between San Diego and somewhere in the LA area like Santa Monica? If so as stated you need to provide a budget per night.
Fodor's Forums are not Twitter, you can type as much as you want, the more info the better.

The OP did say 4 star hotels. That should give you a clue. And I think she knows Santa Monica is not in San Diego, although she may not know that La Jolla is in San Diego.

San Diego - Embarcadero, Star of India, foot ferry over to Coronado (the Hotel Del Coronado which is historic and worth a visit), the USS Midway (a Navy aircraft carrier now a visitor museum), Balboa Park and SD Zoo, Old Town, Pt. Loma Lighthouse, SD Downtown Historic Walking Tour, etc.

La Jolla - kayaking, diving (deep sea and scuba), surfing, walking on the beach, watching seals and sea lions, etc.

>>The OP did say 4 star hotels. That should give you a clue

Hotel budget is $250 per night. Three nights in SD/LaJolla area. Someone suggested Catamaran Resort. Visit Zoo, Midway ship, Del Coronado. What else? Traveling 17 and 10 year old. Then travel north. One night in Long Beach at Hotel Queen Mary? Then 2 nights in Venice Beach at Airbandb. Does this sound ok. Any other ideas. This is 6 days in February

Don't bother spending a night at the Hotel Queen Mary; the old girl is getting a bit worn-out and will be going through a major multi-year refurbishing shortly.

A visit to the QM is well worth it, but since it's only a 90-minute drive (tops) to Venice, make it a day trip from there. Get to your AirBnB, have a fun day/evening up there, work in the trip to the QM subsequently.

Weather could be a major issue, or not. We don't handle rain well in this part of the US, so getting around can be a hassle. However, it might be absolutely lovely. Nothing surprises me any more.

Might want to read up a bit on Venice Beach, it has a very prevalent drug culture plus can have homeless problems. Personally I would rent a place in Marina del Rey (short term rentals are illegal in Santa Monica unless the owner is living on the premises) and walk or bike to Venice.
Agree with rjw about the Queen Mary, and have stayed there several times in January for a dinner dance, it has gotten quite rundown sadly, also the rooms vary a bit.

Catamaran in San Diego is a great location and hotel. I would also recommend it as my first choice:

https://catamaranresort.com/

The Catamaran is in Pacific Beach which is close to La Jolla (maybe a 5-10 minutes drive into the downtown area of La Jolla).
In the heart of La Jolla is La Valencia:

http://www.lavalencia.com/#gref

And further afield is Estancia but also in La Jolla:

http://meritagecollection.com/estancialajolla/

>> Visit Zoo, Midway ship, Del Coronado. What else? >>

You won't have a lot of time with only three days but here are a list of ideas

San Diego Zoo which is part of Balboa Park which has numerous museums (science, natural history, Old Globe Theatre, Air and Space, art and photography, etc, etc)

Pt. Loma Lighthouse,
https://www.nps.gov/cabr/learn/histo...point-loma.htm
Old Town,
http://www.oldtownsandiegoguide.com/
Birch Aquarium (if you have young children other wise I'd skip)
Take a boat tour of the harbor,

do a ocean kayak tour
https://www.lajollakayak.com/