I haven't kept guinea pigs since I was a kid myself - many, many moons ago! So my knowledge is out of date.
Back then, I was told and kept them in minimum of a pair, like a couple of females together, a male joined them for mating, then removed the male. But the craze for keeping rabbits and guinea pigs as indoor pets (back in my day, they were in hutches in the garden, and I was spoiled since my dad build large runs in a shed just for my rabbits and guineas - my house growing up sounds a lot like yours, tons of pets since parents were also animal mad) but I've heard since that guineas are happier in groups of like, six or more? Don't take my word for it, do some research, have just seen the odd adorable video of people keeping them in groups, and it is pretty cute! The logic is that since in the wild, cavies do live in little colonies, and they're a prey animal, so they feel safer and happier with a group of them together.
By the way, baby guineas are born with fur, quite large heads, and little back legs, so they kinda look like furry frogs. Totally adorable and fun for kids to raise them! Good way to learn responsibility, nature, genetics etc.
Check out this herd of them though... think of all the names you could have! Be warned, if you keep them indoors, they squeak all the time...