I would give them a little at a time at first. Mine eat whatever they come across. I'm assuming they aren't salted peanuts. I have almond trees, olive trees, peach, plum you name it and they have access to all of the pits and whatever falls to the ground. I've never had a sick guinea so I think if they want to eat it it's ok for them.
but I think the general rule on this forum is don't feed your birds something you would not eat. My guineas often look at me like I'm crazy when I try to share (awesome) table scraps so it may be a non issue for you.