Try this:
the video, and here is written instruction:
http://fiascofarm.com/goats/bouncing.html
If black mom adopted both babies, at this point, unless grey mom is really trying to take a baby also, you're just going to have to milk the grey doe.
What she has right now is colostrum, milk is out, and freeze it. Make sure to label it as to date what it is and which doe it came from. Milk her twice a day, 12 hours apart.
Save the next milk and freeze it also. Label it as 2nd colostrum. That way if you need some next time around you have it already. It takes my does about 2 weeks before the milk is really great for drinking. Your's might be different. If you don't want goat milk, it will take a bit, but you can dry her off.
As for the black doe, if her udder it still full and tight, you need to milk her part way out also. Your babies at this point may not be able to take all she has (this will change before too long), and you need to keep her milked some so she doesn't get mastitis and it doesn't get too tight for them to nurse from.
I'm going to assume you know how to care for a just freshened doe (feeding, worming, etc). If you don't, let me know. I'll be happy to answer any questions.
