We took DD in March and we let her bring her backpack with a few toys in it, as well as an old tablet that had been repurposed as a video streamer/download device for her.
When we flew United (it was premium economy FWIW) there were a ton of options on the in flight entertainment that were age appropriate for her (just shy of 3 at time of travel), so we really only ended up using the toys while waiting at the gate but we were still glad to have them.
On the way home the in flight entertainment options were ok, not as good for whatever reason, but still sufficient.
One thing that served us very well was on the way there we had one of those mystery bag Disney Princess keychains from Target and she got to open that after we'd been waiting about 45 minutes or an hour, and on the way home we got her a wishable mystery at a gift shop in the parks and same thing, let her open that as a surprise while waiting for the flight.
Besides that, definitely earplanes, DD did very well with them and they certainly helped, though we were having a little trouble with them staying properly seated during descent and so she did get a touch nauseous, but they were better seated on the way home and no issues that flight.
And we brought a few small favorite snacks of hers for the flights too, including a Mickey rice krispie treat on the way home that we got as a surprise in the park. Good luck. The flight from Houston is just a little shorter than yours, and this was more than sufficient for our DD so hopefully yours do well too.