Why did I spend more time on theoretical boning in the first paragraph than the plot? Frankly, the plot isn't much. The kids run around for a bit after their hiding place is blown up, find Clint Jr and end up nagging the Hulk into helping. It's another one of those "watch this if you want something to paint to" cases for Superhero Media. So if you're not keen on reading my harping on minutiae of a stand-alone, throwaway kid's DVD film, maybe skip the rest. First off; Thor. It gets mentioned that he's off in Asgard, possibly being King after the death of Odin, but how the Hela does that keep him so busy that he's fine with letting Ultron murder all of his friends? Seriously, Thor could sort out the whole Ultron problem in a matter of minutes and if he's too busy, Sif and the Warriors Three wouldn't be too much slower. And am I seriously meant to believe that Ultron took down Magneto, Namor, Wonder Man, Sentry and the Inhumans? Bitch, please!
The big battle at the end of the film is actually ok, possibly only because the Hulk gets back into action. A quick look online indicates that there are a couple of tie-in comics and quite a big fan-following, though I really struggle to understand why; sure it's not terrible, but Young Justice and Power Pack are far better. Hell, The Superhero Squad Show is a much better way to introduce younger children to the Marvel Universe, so get on that if you're hoping that your spawn will play some SuperSystem one day.