I'd leave it where it is. Stirring it up again would be the worst thing you could do, because you and they would be breathing it, and you'll never get all of it anyway. Any amount they might ingest is going to be small, unless you laid it down extremely heavily. I'd say let it continue to do it's job down there under the shavings. :)

I'd just wait two weeks from the date you dusted them before eating eggs again. Glad you got a handle on the mites!

Velvet ~:>

Here's a link to a discussion on another forum about the pros & cons of sevin dust. I was particularly interested in the connection to the decline in bee population. I use beneficial nematodes and they seem to be quite effective for most garden pests but you might try one of the other methods for mites on your chickens.

Here is a link that might be useful: sevin dust discussion