We're flying to Mexico in a couple weeks, and I'm wondering whether we need to invest in some toddler headphones. I've seen a few posts on HB about which to get, but I'm wondering if they're even necessary. She won't use them unless we're traveling by plane, so I don't want to spend the money if I don't have to. Sadie will use my tablet to play games & watch movies, but she's usually okay with the sound down pretty low. But, I also don't want to annoy anyone on the plane. One flight is 1.5 hrs, the other 2.5. Opinions?