I know you don't want to use pine or cedar shavings for the bedding. If I'm wrong, someone will surely correct me. I use Carefresh pet bedding. It's recycled paper, with no inks or dyes or fragrance. And, it's really absorbant. But, you'll get more ideas and stuff by searching online, and, I'm sure others will tell you more.

I'd just use tepid water for bathtime, if it's necessary to bathe them. But, they also make bunny bath shampoo that's safe to use on guinea pigs. I used it on mine a couple of times. Just a tiny amount, and, if you do use any kind of shampoo, make sure to rinse, rinse, rinse! Don't get water in their ears or shampoo in their eyes.

And, you should clip their nails. I used to just use regular nail clippers or small dog or cat clippers. They have nerves in their nails, just like dogs and cats, so, be careful! If you're not comfortable doing it, call some groomers or your vet to see what they would charge. And, they can give you advice, too.