Hi Jilly!
Here's an article I wrote about Vaccinations for Cats that explains the main shots they need.
http://www.bellaonline.com/articles/art49756.asp When I worked for my vet we always recommended starting their series of FVRCP vacs at around 8 weeks old.
Re: Momma cat taking the kitties under the house, I agree with Claybird - it very well could be her "litter box" or just a nice, cool place she likes.
When the kitty I grew up with had kittens, we kept one and I honestly can't remember Mitten really pushing Ginger away. It was so long ago that I don't remember exactly how old Ginger was when she stopped nursing. Since then most of the kittens we've adopted have been at least 8 weeks old, so they've already been weaned.
As far as finding homes, in addition to word of mouth, I would suggest making up flyers - with the kittens pictures on it, if possible - and asking local animal hospitals and even pet stores if they have anywhere you can post one. Look for other places in your community to post flyers as well.
Create a Catster account -
http://www.catster.com/ - for the kittens. You can indicate they are up for adoption.
Contact local rescue groups or shelters to see if they will "sponsor" your kittens and list them on petfinder.com. I have seen ads on petfinder before that say something like this is a courtesy listing. It might depend on the group, but it could be worth a try.
I must get ready for work now, but I will post more ideas for you as I think of them. And if you have other questions, please do post them.