Re: cliffs
Ivonia, from what I can tell, I think your ending may be all right as stands. It seems like the major conflict for that one book has ended (dealing with the baddies), but now they have to move on to liberating the home planet, which I would assume is the preliminary conflict on the next novel.
Now, as a forewarning, we've had some threads previously which talk about querying series to publishers. If I have the time later, I'll try to dig up the threads, but I suggest you look for them as well. They should still be hanging around on previous Novels pages. The main problem some people see is that pubs/editors are reluctant to take on series, because if the first book doesn't sell, the second is a no-go anyway.
EGG, "do you consider a character death a cliffhanger?" It kind of depends on the kind of death you're talking about. Have you been reading the Harry Potter series? If so, I'm going to use an example from the 4th novel. Toward the end, there is one sentence: "He was dead." Now, imagine, if Rowling had decided to stop writing then and there. I'd be pretty ticked off, but there's a cliffhanger for you. Both her 4th and 5th novels "end" with character deaths. The one in the 5th book, while not a cliffhanger, leaves lots of questions surrounding the death, while the 4th novel's death had nothing questionable about it. Of course, while using Rowling as an example, we'd have to acknowledge her devoted fan base. Her following books will sell no matter what cliffhangers she uses now. Do you think anything would have changed if she'd use these methods in the 1st novel? Hard to say.
Anyway, I'm always sorry to bring up Rowling as an example. I feel it's a commonly used example, even though not everyone reads them. I hope you have, so you know what I'm referencing.
As for me, when reading a series, I tend to get nervous toward the end of the book. I hope all of my questions will be answered by the end, which is what Uncle Jim mentioned earlier in the thread. As long as the bigger plot is taken covered, I can handle it if the author leaves some smaller plotlines to follow later -- especially if the author hints it will be resolved later (ie: "I'll tell you when you're older").
I hope this helped you, at least a little!