The question is not whether one has experience with little children but whether medically, headphones and flight noise are good or bad for the sensitive hearing of children and especially toddlers. The answer to that is clear. The decision to act on this information is up to the individual.
Obviously, there are good videos for children, and I myself think that I learned a lot from watching TV. But when you see how much screen time children get nowadays between TV, computer and video games, any minute that they do not spend in front of a screen but with human interaction of any kind (except being beaten) is valuable. FYI, I do not own a TV anymore and don't miss it one bit. But you'd have to pry my internet connection out of my cold dead hands. And I also have a major home-theatre installation on which I watch 2-3 movies of my choice per week.
While I think of myself as an educated person, and I can back that up with the necessary diplomas and stuff, I would not think that I am able to home-school my children at the level that a good school can do it. If I lived way out from civilization that might be an option but not if I can avoid it. As someone dedicated to teaching (at university level), I know that certain methods can actually lead to good results for certain purposes. So I wouldn't want to rule out educational videos as bad.
The 2 parents/1 child proportion was referring to the OP's situation in this particular case.
Obviously, I do not suggest people stop flying with children, though I admit it would be wonderfully considerate (evil grin). But I think my advice and documentation on noise levels and hearing damage are worthy of consideration for parents who want the best for their children, which is certainly the case here. I'd clearly use a little wax ear plug for them. They can be molded to just the right shape and size so they won't put pressure and won't hurt. The attenuation achieved with this is probably in the 10-15db range. The best ear plugs for adults get around 30 db attenuation. But the 10-15 would already be enough to protect the baby's/child's hearing. The child will not be in acoustic isolation and will still hear what you say to them but there will not be any danger of hearing damage anymore. I think that is a good compromise, no?
Actually, I recommend even to adults to use plugs. I do and it makes flying much more agreeable and less stressful. The important thing I have noticed, as I said, is to only use them at cruising altitude. Otherwise, there can be painful pressure exchanges.
Besides, that themicah might want to check out
www.head-fi.org and ask the question there. These guys and gals are total "can nuts" and can certainly be even more helpful.
Till