In reply to pasbury:
I have 2 small children and I think they watch a bit too much TV, including on a tablet, but at least it's only at home and we do restrict exactly what they are watching and for how long. It is very easy to plonk them in front of Octonauts/Peppa, though, when you do just need 10 mins to get something done and my wife is also busy. At least BBC iPlayer doesn't have the adverts that YouTube does and they do tend to watch a lot of DVDs, which also don't.
On the other hand, their imagination does get a lot of fuel out of it and stuff like Chitty Chitty Bang Bang has been role-played to death.
They NEVER watch anything when we're out of the house or in the car as a family - we play games in the car and have a supply of paper and crayons in the bag if they're bored.
One of the mistakes I made was letting my daughter watch something on my phone - equally, the best thing I did was, when that one broke, telling her my new phone didn't have YouTube. She's never asked to watch anything on it since
I'll get my wife to do the same next time she gets a new phone.
We also make it quite clear that they can't have whatever they want, whenever they want it. Older daughter had a mini-meltdown on Saturday over something she wanted in a shop, but was told she couldn't have it, with reasons why.