I hope some of the 80 year old parents that posted 1-2 years ago about children and iPads are still getting updates to this thread.
My son who is almost 22 months can operate the iPad fine, he's worked out how to unlock it and open the app that plays his favourite Elmo movie and he knows where the play button is. Since he watches no TV we figure the occasional Elmo and Disney video and Sesame street songs will be ok for him.
We are quite happy to let him use our iPad 3rd Gen's with mild supervision, but we won't take it from him if we get up to use the toilet or get a drink. We have told him what he is and isn't allowed to do with it and he respects that and follows it. All you have to do is give them reason to trust you and your judgement completely and make sure they understand why they mustn't do something. It helps that he is very advanced for his age but I cannot see why your average 24-28 month old wouldn't be the same.
He has been playing a bowling and motorbike game on occasion on our iPhone's as well for a few months and again we trust him with it. Good education and trusting your child can go a long way. We've even trusted him to carry the phones and other breakables around and asked him to take the iPhones to the other parent and never had a problem. I think it's sad when parents cannot trust their own children! Where and who have they learned their traits from? Perhaps it says something about their primary carers if they have learned to be untrustworthy.
We will most likely make one of our old iPad 2's his exclusively in the coming months. I should mention something that I think helps him understand loss of something he breaks; he learnt what the bin was not long after he could walk, and that anything that goes in there never comes back. So when he breaks a toy beyond repair (which I think has happened maybe once or twice ever), we told him it was broken (which he already understood by then) and that we couldn't fix it (also which he could understand), and it had to go in the bin and let him do it. After doing this with a toy he played with, and without getting upset I believe that he understood that he needed to look after his gear or he'd lose it. He trusts that when we tell him to not do something it's for a good reason and listens, but we always give him an explanation he can understand at least once.
How can they learn responsibility without a chance to be responsible? Besides, any lesson you can teach a child is worth more than what could potentially get broken if we're talking about material possessions. What is more important than a child learning and being happy?
Call me a bad parent all you like friends, I'll try not to be upset about it while my child outshines yours and lives a successful life. Embrace the best years that humanity has ever been lucky enough to have as they may not last.