So many issues I see with parenting come from parents wanting a quick-fix solution, and that can be either with parents just caving to their kids requests to make them shut up, or parents getting all angry and shouty just to make them shut up. They're two sides of the same coin - want solution now - just shut up! I'm sure that this comes to news as nobody here, but behaviour management (either for my own child or other people's children (my students)) comes down to 3 key factors:
* Be firm
* Be fair
* Be consistent

This is why the actors in that WWYD video are failing as parents because they're failing to observe all 3 basic principles of parenting. Simply asking the boy to put his tablet away instead of telling him to do so is soft, not firm. Yanking the tablet away from him without giving any warning or opportunity to do it himself is unfair. And obviously they're not being consistent with their expectations... children will use devices at the table because they've been allowed to do so before. They've gotten away with it before.

Grandparents can be tricky, but I think the best thing you can do is ensure that you and your wife are being as firm, fair and consistent as possible with your child at home. You will find that that will have a greater effect than grandparents anyway. Worst case scenario, your son will only be indulged with greater screen time at his grandparents' place but nowhere else. Children will modify their behaviour in different situations and for different adults, but ultimately it comes from the parents. And especially during the Terrible Twos... man do I not miss this period! But seriously, so long as you dig your heels in deep and maintain the core principles of parenting, then things will get a lot better by Age 3.

My nephew is now 3½ and he already started entering the Terrible Twos when he was 1½ - and yeah, part of that was due to grandparents badly spoiling him. But his parents dug their heels in after his 2nd birthday and now he's so different. When he was 2 he was a real handful. He'd run into oncoming traffic if you didn't watch him, and his mum and dad were constantly chasing him like in an episode of Benny Hill. But he's changed so much now - he was playing with my daughter on the weekend and they were playing with Nerf guns. I told him that he could shoot objects but never shoot people. For the most part he was good with this rule, but then he went and shot someone else. Now it didn't hurt, but he broke the rule so I confiscated the gun from him. I was expecting him to have a meltdown, but he didn't! He put himself into a naughty corner! I walked away from him and started counting down to 3 minutes of isolation (1 minute for each year of his life), but after 1.5 minutes he walked over to me and apologised. So I did the follow up talk -- crouched down to his eye level and asked him what he had done blah blah blah, then kisses and cuddles and praised him for owning up to his behaviour. And yeah, our daughter was a terror at 2, but we dug our heels in and behaviour-wise things have been pretty smooth since age 3. Seriously, my current behaviour target for her atm is that she still chews loudly... but this made me realise that if loud chewing at the table is my biggest behavioural concern for my child, then I'm not doing so badly.

One thing that interested me about gamblor916's experience with watching Bumblebee vs my third viewing was that in both cases our cinemas were full of school kids on holiday care. So they were away from their parents. But gamblor916 mentioned that the kids in his cinema were well behaved, whereas the kids in my cinema (and Tha Phantom was with me and can vouch for this) were just excremental. But this just goes to show that the kids in gamblor916's cinemas have been demonstrably better parented than those in my cinema. Because a well parented child can be trusted to behave themselves even when their parents aren't around. If a child only behaves themselves when a parent has to be there to threaten them, then the child isn't really a well behaved child. They're a rotten child who is just waiting for an opportunity to misbehave, and that opportunity may be when mum and dad aren't around. And of course, you have super bad kids who will outright misbehave in front of their parents.

Note: I'm not talking about occasional misbehaving. Kids and kids and will sometimes make mistakes. I'm talking about routine or regular misbehaviours. My daughter hasn't yet attempted to use her tablet at the table, but she's only had it for a few weeks. But if she becomes the kind of kid who can't put her tablet down then I need to reevaluate my parenting practices!