You'd have to decide whether you're going to stick to Texas and the West Coast...or fly to the East Coast at some point in your trip.
I'd fly from Houston to Phoenix, rent a car and drive to the Grand Canyon, Las Vegas...then to LA...then to Santa Barabara / Solvang (wineries), Monterey (Monterey Bay Aquarium) and then to SF and the Bay Area. Maybe a day or two outside of SF in Napa/Sonoma (wine country / balloon ride). If you were going in a warmer time of the year, I'd recommend going to Yosemite and gold rush country but not in March...
You could fly from SFO to somewhere on the East Coast (NYC, DC, Florida). As others have posted, the Georgia Aquarium in Atlanta is great. So is the National Aquarium in Baltimore (an hour from DC). The Amazonia Exhibit at the National Zoo in DC has a great Arapaima display and of course lots of great museums in DC.
Matt