It is heavily implied that the kids could move around, they just weren't as effective as they would be under normal conditions. That argument also does not discredit their durability, and we've had several scenarios where stronger characters utterly humiliate weaker ones. Most of these examples contain gaps that are far smaller than Android 18 would be in comparison to the suggested battle power of Goten and Trunks. Further-more, if they could also throw punches and block her shots, they would have no trouble doing so after receiving a 50x times boost from their Super Saiyan transformation. It is not even a reliable argument, it's a fuckin' cop-out at best.
For these types of illogical perspectives to be true, requires us to ignore essentially every power related gap that we have ever seen in the entire series. It's not consistent within the story and it is not even self consistent for that matter.
I'll prefer to stick to my own analysis until I see something more convincing.