Guinea-Pigs ARE great
and shiny I suggest you sit yourself down with a large drink and read some of the back threads on Super Furry Animals.
Some things I'll pass on to you though.
I got my first guinea in 1974 -sow. My brother got one 3 months later -sow.
Mine wasn't a sow . We had piglets.
So, first, make sure that they are checked. 
We have two boars at the moment. (An adult, the survivor of two brothers, and a 9 month old )
We got the brothers from a Rescue, my daughter wanted boars.We got the piglet from a Rescue (I needed a baby boar to match with my lone adult)
Sows are easier though.
They need much more space than you'd imagine. Lack of space and boredom makes them narky (especially boars)
I use hay and newspaper as bedding.
Indoors they might have cotton bathmats or towels but they're a pain to wash (hay in your washing machine) unless you put them in a pillowcase.
You need to protect them. Damp, cold, extreme heat, draughts, foxes, cats.- all dangerous to guinea-pigs.
Make sure your DS isn't allergic to piggies or hay.
Read up on the things they should or shouldn't eat,
Have a look at the "Show your Furries" thread, my handome beasts are the ones in Santa Hats
. They are only forced to do this once a year.
Though DD put her GP1 in a Build-a-Bear Skater dress and he has never stopped sniping.