That’s a bit harsh to a new member,a real welcome to the forum!
I did notice that. I wonder if they joined the forum to troll, but certainly I will not give any time to anyone, whether on their first post or 10,000th, who believes that deliberately annoying other passengers in order to get what they want is in any way acceptable, because it isn't.
I quote again:
Passengers with reservations tend to be resistant to moving for any reason, even when the situation is explained and they are asked politely, so the kids all got an iPad as noisy as possible in the hope that we’d eventually be able to sit near the kids.
This is utterly inexcusable and unacceptable self-entitled, selfish behaviour. If the OP feels that way they should travel exclusively by car.
If you want others to move, you ask nicely. Or you approach traincrew, who may help. You absolutely
do not act in breach of a Railway Byelaw to the deliberate annoyance of others in the hope that they move. Ever.
The trouble with children is that unless they’re entertained in some way they become more irritating to others so watching an iPad is probably better than having them running around and shouting/screaming etc.
No excuse. Simply use headphones. If you can afford an iPad you can probably afford fancy ones, but if not they can be had for about £5 on eBay or Amazon. You simply do not play devices out loud in public, end of.
What the OP did is a Byelaw breach (or would be if I were on that train, as it would 100% guaranteed be "to my annoyance"). It needs prosecuting, not excusing.