Notice that you're a human but you care about that. If there weren't something in human axiology that could lead to sufficiently smart and reflective people concluding that nonhuman intelligent life is valuable, you wouldn't have even thought of that — and, indeed, it seems that in general as you look at smarter, more informed, and more thoughtful people, you see less provincialism and more universal views of ethics. And that's exactly the sort of thing that CEV is designed to take into account.

The same argument applies to just using one person as the template and saying that their preference already includes caring about all the other people.

The reason CEV might be preferable to starting from your own preference (I now begin to realize) is that the decision to privilege yourself vs. grant other people fair influence is also subject to morality, so to the extent you can be certain about this being more moral, it's what you should do. Fairness, also being merely a heuristic, is subject to further improvement, as can be inclusion of volition of aliens in the original definition.

Of course, you might want to fall back to a "reflective injunction" of not inventing overly elaborate plans, since you haven't had the capability of examining them well enough to rule them superior to more straightforward plans, such as using volition of a single human. But this is still a decision point, and the correct answer is not obvious.