Mites Is this ok for my boys?

Do they have mites, lice, or fleas? I would (if it were me) get another shampoo that is just regular. You can use kitten safe shampoo or small animal shampoo, or in a pinch a little oatmeal dog shampoo would be ok, but of course kitten safe or small animal safe would be best

I haven't seen any but I thought it be ok to give them a treatment to be sure? Xx

No, no insecticidal shampoos. They're very harsh on the skin. That shampoo won't protect them from any of those pests if they don't have them already, and if they do, there are much safer ways (for the guinea pigs) of killing them.

You need a shampoo made for small exotic critters -- one for kittens is fine, or for small exotic pets. You should be able to get one online if you can't find one locally.

I love (broken link removed) Shampoos. They're a real treat, and all using natural products so quite safe.