Science Fiction book where aliens save the planet by crashing a meteor into earth

[Ben]

Sorry if this is a little vague (Also I might have mentally combined 2 books here) the book was written and publised before 2012 if that helps

A scene in the book has some kids who are planning to overthow something (Either an organisation or the government) so they go into a secure+sound proofed room to plan, putting a robot on guard outside the door. But then someone finds out and kills all of them (for planning against said organisation), except one, who fell and pretended to be dead. The kid realises too late that the “servant” robot who did things like make tea and stuff was actually there to make listen in on the people and prevent them from doing anything wrong.

Then later aliens arrived and people get really panicked and end up shooting one of them. Eventually the aliens use a combination of alien tech and human tech to go past the speed of light and go into the past, to launch a meteor at the earth to kill the dinosaurs. (I think) they do this because their race is close to extinction so they sacrifice themselves to save us.

Sorry again for how vague this is. I really remember enjoying the book, but I can’t remember much else about it and want to read it again.

[Kris]

Ben, can you describe the kids' society and why they want to overthrow the organization/government?

Can you tell us more about the kids - how many, their ages, genders, special skills/powers, family/friend, etc.? Where do they live and with whom?

[Lobstergirl, au gratin]

Ben, are you still looking for this or did you find it?

[Ben]

Still looking XDDDDD
Or rather hoping it just shows up out of nowhere XD
It was a book I read in primary school and I am somewhat eager to reread it XD