I'm partial to Florida.
In South Florida, you have the Keys, the Everglades and lots of various attractions in the tri county area of Dade/Broward/Palm Beach. Those can all be day trips - or you can venture farther down the keys for an overnight trip. You could do a day trip to the west coast and check out Naples or Sanibel Island (I remember lots of bike rentals there - family style bikes where babies/toddlers can ride on the bikes). This time of year, the parks are nice to visit - lots of great parks. Even beach time is in the cards in March in South Florida. The water is so much warmer than Pacific Coast beaches. A few hours north is umm...what's it called in Daytona Beach...NASA place.
Of course, leave it to me to remember the mall stuff.

There is a pretty big mall near Ft Lauderdale - I want to say it's the shape of an alligator. I remember it has a Rainforrest Cafe and tons of stores - almost a "great" mall kind of thing. There is an IMAX in Ft Lauderdale and a museum - wanna say a Discovery type museum. You can take a tour of the intercoastal and they show all of the fancy-smancy homes that cost 2 zillion dollars (but then you can get that in our own Bay Area too!).
Some other kid friendly places I remember from the area...
Butterfly World - thousand of square feet of butterflies and sub tropic feel to the whole place...I wanna say right near there you can ride horses and I think they have ponies for toddlers.
Lion Country Safari - you drive thru and look at animals. Think there is park/petting zoo. ??? Can't remember about the zoo.
Miami Seaquarium
Parrot Jungle Island
In Boca Raton (where I lived), there was Gumbo Limbo, a nature center near the sea w/ hands on stuff. Also, Morikami Museum and Japanese Gardens which is kid friendly.
I know many good restaurants that I miss so much. Banana Boat in Boynton Beach and Cap's Place Island Restaurant (really an island where you park and take a short ferry ride to get to restaurant) stand out in my mind.
There is often various entertainment around south Florida- concerts and stuff.
You can take about a 3 hour boat ride over to the Bahamas for the day. We did this about a month before Elisha was born. We rented a cabin on the boat for a slightly higher ticket so we had a place to rest during the trip to the island. Entertainment on the boat.
I am sure there are rentals around the area where you can just chill out and enjoy the nice weather. Sun, sand and sea.
*sob* I miss Florida!