With the exception of snow sports, you can quite literally find anything to do in Texas that there is to do. I would offer one caution though, as it pertains to beaches on the Texas coast. Don't waste your time. If you live within a half day drive of south Padre Island (this alone rules out most everyone not living in Texas) then go there, but if a nice clean sandy beach and warm water is what you have in mind, go to Florida, Mexico, or elsewhere. San Antonio is nice and the kids would enjoy Sea World and Fiesta Texas. You and the wife would probably enjoy the river walk. You mentioned the Woodlands, which is nice if you like to golf. I'm not sure what the kids would like there other than a nice resort swim pool, but March in Houston may not be swim suit weather quite yet. Many, many more options throughout Texas, but if you can give a better idea what you are looking for then we can direct you a little better. Keep in mind that Texas in March and April could be warm or quite cold.