But now the readers can cut out a large percentage of potential endings! Now they know that [spoiler]the characters won't end up okay.[/spoiler] Now they know that [spoiler]the ending's a little bitter.[/spoiler] Yes, it's ambiguous, but it sparks a number of assumptions!
Additionally, it doesn't matter if you don't give the parties involved. It won't come as much of a shock. I might have cried reading that in [spoiler]The Ellimist Chronicles/The Beginning[/spoiler] had I not heard it a million times. Ever seen the trope "Viewers Are Morons?" Unfortunately, they aren't. Don't underestimate the power of guessing.
On another note, [spoiler]what happened to the Yeerks after The War? I know what happened to the ones invading Earth, but what about the rest of them on distant planets? Is the Pool Ship the main Yeerk ship? I thought it was one of many.[/spoiler]