I'm sure you'll be fine. I've never been to the Texas one, but we go to our local Six Flags all the time. If schools are still in session, you'll likely have very light crowds. UNLESS perhaps schools are having any field trips that day. Although usually, for big trips, the park is closed for a special day. Really no need to plan anything. Take a look at the map before you go and get a general idea of what you want to see. Perhaps walk in and go to the left (I think many people just tend to go to the right--generally speaking). And just go in a big circle.
I'm sure they'll do a child swap for you. They do that at ours. Everyone stands in line and then when it's your turn the people staying behind will have to wait in the exit. Not sure what the switch pass is though. They do have something like a fast pass, but I think you have to pay for it. I've never used it. You likely won't need it.