OK.
Listen carefully.
I have three words for you.
PORTABLE DVD PLAYER.
Trust me. It'll be the best $$$ you'll spend.
My daughter (who's 11) just saved up and bought herself one (she didn't want to wait till xmas) as we drive about 6 hours every weekend. It's fantastic. She watches a movie on the way there and another on the way home.
I know your kids are much littler, but, even if it's only for the 3yo, it'll be fantastic.
I recommend if you ARE going to get them a screen each, buy two separate units. There's nothing surer than they'll want to watch two different things if you get one of those systems with the two screens. Besides, with separate units you can have them watching them on the plane.
The one Stephie bought was from WOW, and it cost $130. it's a 7" screen which flips around onto the unit to form a sort of tablet. It's very good value and very good resolution. She's thrilled (and so am I). Also it seems quite robust, and comes with a case and car charger (as well as the normal power cables and batteries), also I'm told you can get a replacement battery for it if required.
Being 1 and 3, they're far too small to care what's going on out the window, they won't read books (even if the older one looks at picture books for a while, a movie will keep them busy for much longer).
Oh, and, if you are going to get two of them, make copies of your DVD's and take the copy along too, so that you can allow them both to watch the same movie if they want in their own player.
Good luck with the trip.
Oh, one other piece of advice. Get a good camera. I'd recommend a Canon 400D with two main lenses:
Sigma 12-24 and a
Canon 28-135 IS USM lens. The former lens will be invaluable with landscape shots, and there will be LOTS of those in USA. The second one is a great all-round lens magic for kid-type photos. I haven't recommended a zoom lens, but I'd go for a Canon brand one, they do a really great zoom lens, but the Sigma lens is MUCH better on the wide stuff. If you don't want an SLR camera, look at the Panasonic Lumix FZ range.
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