Thanks for all your inputs, still have some thinking to do, I might even just ask our oldest what she would prefer. She is 7 1/2, very responsible and careful with all her things. She has taken good care of my old Sansa Fuze and Sennheiser PX100, also has taken good care of her leap pad for 2 years, but has pretty much out grown it. I have no concerns with her having a tablet with a case, she loves reading and could use it for books and searching for school work. The other 2 I am not as sure, but it is hard to buy one thing for one and something different for the others, they like having the same.
I have also come across the Asus memo pad HD7, essentially identical to a 2012 nexus 7, which Asus built, but with a 5mp rear camera, 16gb internal and a micro SD slot. The kids like to take pictures and movies so the camera is kind of important, but they are not into massive games so processor power is not as important
After myself taking apart and reassembling 2 iPhone 4 devices, there is no question about the build quality and materials, which is part of the price difference in similar size devices. I absolutely do not expect a tablet with Apple build quality for a Asus price, that is simply one of the compromises. A iPod touch in a otterbox defender is almost indestructible (all of our phones have otterboxes and we have never cracked anything) But I think a Asus tablet in a heavy case would be durable too, our kids do not throw stuff or step on it, just occasionally slips from hands.
Also, all devices have limits to what OS they can run, this is a fact of life The iPod Touch 4th gen, the ones we are looking at, are stuck with the last update to iOS 6, they can't do iOS 7. Our 1st gen iPad is stuck with iOS5, and I wish I could take it back to iOS4, 5 really bogs it down.
Again, thanks for all your experiences
Daniel