I vote for the Sheraton too.
Your kids @ 6 and 8 will LOVE having dinner at the Corvette Diner in Hillcrest, a short drive up the hill from Mission Valley. It really is a fun place with great food and losts to see/do hear. There is even a DJ booth where they will take requests for music played over the PA. Don't miss it.
If you are a member of Costco, there is one just opposite Legoland and they sell discounted ticktes in the Costco that will save you a bundle. Also, by the summer, Entertainment books will be half price and it is worth having one for your visit here.
Send me PM if you need/want any other tips.