Thanks for all of your input. It hadn't occurred to me to move my older son until another mom told me she'd have to pull her daughter if her son didn't get in. And I thought, huh!
They do have some common friends, and although it's a magnet, it's the neighboring school so we do have a lot of neighborhood friends at the magnet. Which is why I fear DS5 will feel like he's been exiled.
I'm not totally sure the magnet is all it's cracked up to be either, but since I don't have a good comparison...
Hopefully the transfer will come through and we won't have to worry about it, but thank you for sharing your perspectives. I think we'll leave DS7 where he is, as long as that is what he wants, too.