AS you managed to upload a few documents and showed the money in the bank, I can not see any problem to show them again at immigration, to get a 180 day Extension of Stay.
Same documents, so if they where genuine it is a piece of cake.
The reason you got this stay changed and as you signed to inform the Immigration officer when that happens, why do you think you are allowed to change the rules?
If you apply for two people on the same time, you upload a screen shot of the main application, be aware that a reference number/application number is visible on that screen shot