yes. it always annoyed me pre-kids when people let their children listen to videos or play games without headphones so i do it as a kindness to the other passengers. practice before the flight so they are used to them.

Our toddler uses these:
http://www.amazon.com/JLab-JBuddies-Volume-Limiting-Headphones/dp/B007VL90AW/ref=sr_1_11?ie=UTF8&qid=1387384069&sr=8-11&keywords=toddler+headphones

I turn the volume on the device to high and then set the headphone volume (turn dial on the right ear piece). DS is far likelier to accidentally adjust the device volume, so I can be reasonably sure that he's not blowing out his hearing. They're sized appropriately for small, child heads, and the cushioned cups fit well on his ears.

We tried smallish headphones (the kind that sit on your ear, not inside and not big cups) and DS wouldn't wear them, so he used the iPad without sound. Then we discovered he loves my noise-canceling headphones (the kind with big cups that go over the ear) even though they are ludicrously big on him, so now he uses those. I always put them on me first to set the volume and check at intervals that he hasn't changed the level.

Yes. For the love of god headphones. I wanted to strangle the couple (no kids) sharing their iPad to watch movie.

Headphones, and when she takes them off, no volume.