where to stay in San Diego if we want to visit Legoland, Seaworld, etc. Looking for nice accommodations...

Marriott Marina is one of their best hotels with a spectacular view, walking distance to gas lamp district, and a very nice pool.

A little more detail other than "nice accommodations" would be helpful. Something like preferred location, budget,things you'd like to be close to (eg restaurants, shopping, beach).

Legoland and SeaWorld are not next to each other, or even close to each other, so there is no hotel which would be convenient for both. You'll have to drive to one, and it would make sense to stay in the general area where most of the sites you'll want to visit are located, or are close by. That would most likely be La Jolla, Downtown, or Mission Valley.

You will need a car.

Nice accommodations means different things to different people. How much do you want to spend? Will you have a car? When are you coming? Prices vary greatly based on dates of your trip here.

Check out the Catamaran on Mission Bay; while very convenient to Sea World and Mission Bay activities, it is also a quick walk to the oceanfront walk and beaches in Mission Beach and Pacific Beach. You will need to hop on the 5 from Garnet Ave. north to Legoland, or cruise up along the 101 where you can stop at several lovely LaJolla beaches; avoid downtown LaJolla if you can, it is bogged down in traffic an tourist shops, but some great restaurants; while at Legoland, check the Flower Fields just slightly south in Carlsbad, the kids enjoy that, esp. the tractor rides around; ride south along the 101 stopping perhaps in Del Mar, there is a nice playground and park right off the center of town. But I can't tell you the current rates at Catamaran, lots of grass to play on, find loads of parrots/birds, great for strollers and bikes and rollerblades to zip around the bay or boat ride across on the Bahia Belle, loads of great sandy beach. Explore the La Jolla caves from La Jolla shores (just north of town) and have the loveliest and delicious breakfast or lunch the Cottage, also in LaJolla (and great for kids). Another hit is Moonlight Beach in Encinitas where you have a great playground at the beach with showers, picnic tables, right off the 101. What month are you planning to go?