My kids use my and their dad's iPads all the time and we've had no problems. The older one (10) has her own Nook Tablet with a N2A card and has had no problems. I have no problems with kids using tablets.
I think Apple is better than Android, but of course iPads are more expensive. I don't know that larger is necessarily better for games though. Everything is just smaller and it doesn't seem to bother my kids. They prefer the iPads but I think it's due to what games are available, not size. My daughter does a LOT of reading on the Nook Tablet, though, both when using it as a Nook, and on the Kindle app when using it as an Android tablet.