Soon to be New Owner of a Piggy

we hope. We went to Petco today and the kids were looking at piggies, hampsters and the one chinchilla they had. My husband and I were talking about adopting a hampster because they had some for adoption, not for sell and they are cheaper to care for then piggies. One of the associates over heard us and said that someone was bringing in a guinea pig soon with the cage and everything she had, because she had become to sick to care for her pet. We told her we would be interested. I had 4 guinea pigs as a child and my husband and I had 2 before we had our first child. I am pretty sure I know how to care for the newest member, should we recieve him or her, of our zoo. But I would like any and all advice. We had the normal cage and a guinea pig ball for our piggies back then. We changed thier cages every week and fed them the guinea pig food and treats. I also know how to hold them. This guinea pig, or pigs will be my childrens pet in our homeschool class room. They also have 3 whites tree frogs, a 55 gallon fish tank, a cat and a dog. I care for all thier animals though I do force them to feed water and clean up after the dog and cat. I want them to be largely responsible for thier new pet as long as I am present. They are 6,5, 3 and 2. I dont want them ever to open the cage without me or thier father present. I know how to teach them that much. But all advice is welcomed. Thanks.