Are you wanting to avoid crowds? I presume so, The Houston Zoo is great, The Clear Lake area with the Space Center and Kemah Boardwalk is a NIGHTMARE during spring break. If you don't mind the drive to San Antonio then Sea World is a unforgettable experience. Oh, the Children's museum near the zoo would work real well.
I would also suggest at trip to San Antonio area. My Daughter and her husband took their 2 girls (8 & 12) there last year and stayed five days. The girls never complained once about being bored. Plenty of outdoor activities and sightseeing for the entire family.
Dave & Pat
1999 Wanderer 230FB
2004 F250, XLT Crew Cab, V10, finally, enough power!
"No kids, no pets, trying to make it to retirement"
Having lived in the Bayou City I can safely say that any trip "from Houston" will be a darned sight better than any trip "to Houston". I say that with a big grin because we still have a lot of friends there and are due for a trip. A side visit to NASA would also thrill my two boys.
There are several nice places in the Hill Country/San Antonio that may peak your interest. If you don't mind being near water (could be an issue for you with the younger ones), most of the many parks up and down the Guadalupe River between New Braunfels and Canyon Dam will have openings that time of year. There are several attractions that you could branch out and see from there like Natural Bridge Caverns, Sea World, Riverwalk in S.A., etc. The Kerrville area (including Fredericksberg, Bandera, Medina, etc.) is also nice and you can pick between riverfront parks and those in a more ranch-like setting.
We will be camping fairly close to home during spring break. We are going to the Dinosaur State Park in Glen Rose. I've never seen the dino tracks in the riverbed. That should be a hoot.
Last fall we went to Rusk State Park where they have the Texas State Railroad. The old trains weren't running at that time due to the funding dispute with the legislature. I think they have obtained a combo of public and private funding to get the trains going again. We loved the park and the peace and quiet of the non-crowds. If the trains are running again it may be hard to get a spot unless you book early.
I'll stop before I start sounding like a commercial for Texas camping. But you really have to try hard to have a bad trip in this state. There are so many options that you could spend years without scrathing the surface of the possibilities.
Anyplace they go on vacation in the RV will be memorable. At that age feeding ducks, looking at the stars, making a fire and cooking marshmallows, collecting sea shells, collecting pine cones, all are wonderful. All they really want is your undivided attention. Enjoy them while their young.
If you end up heading towards the coast, these are proven winners with our kids when the boy was five and six and with a one year old girl (she didn't care for Gaido's too much).