Yep, I'm late, but I did just now finish the series, and here is my speculation on several items:
[spoil]Where to start... Ok, the crow, I didn't get, but a few things I can piece together (yes I know Clannad was after Air, but bear with me), In Clannad, ~After stories~ it turns out Tomoya was the robot, but he couldn't build or do anything but spectate this girl, and Yukito was eventually reincarnated as the crow with a somewhat similar role.
The "looping" as I saw it referred to as, made me pissed to, but it makes sense when at the beginning and end the lady says the story will continue forever without end, until the last child. A.D.D. MOMENT: And how all the winged girls wanted to just do something fun like go to the beach and how all Yukito had to do was make Misuzu smile and stay by her side; anyway, all the memories will be passed down from child to child, to the very last UNTIL THE LAST MEMORY IS FULL OF NOTHING BUT HAPPINESS.. <---- That I believe is THE BIGGEST POINT, especially in other Key films, like Clannad with the Hikari and Angel Beats!
The two children at the end, I had a theory, and it was Yukitos mom, since she promised to return, but thinking about it, I saw another post, and it was Yukito and Misuzu, interesting thought, and may as well be true, even more so now because the sequence begins with the "listen here my child..." and the boy on the beach snaps to and "remembers it from a long time ago".
It was sad/funny when Misuzu kept falling over, even more sad so when you figure out why.
I had another thought, but it slipped, I'll edit it back later.
Heres my along waited edit...
So, I started Kanon (the 24 ep. version) a little while back and just figured out that Yuichi Aizawa's child voice (for English dubs) is the same as the little boy's voice at the very end of Air, also, if you look closely, there hair color is pretty close and FINALLY, the girl he is hanging out with on the beach has the same hair color (and sounds like) Nayuki Minase... Interesting, don't know if this has anything to do with either story, but it may just be a cross over, as the sloth from Air is in Kanon as well.