Like a lot of animals, they're much happier when together with their own kind. It just isn't the same for them having company only from people.
It's the same amount of time feeding, cleaning, playing etc. But you'd actually have to spend less time with 2 than with 1 because they'd have each other to keep each other company. It would be more food, but their food is very cheap really.
I'm not trying to be mean because you didn't know that they should be kept in pairs, so please don't think people are trying to be mean, they're just wanting to let you know.
If you can, then show this website to your parents and they'll see all our replies saying guinea pigs are much much happier in pairs.
They're much more fun when in pairs, because they run around and squeak to each other and stuff. If you have one on its own then it might just sit there and do nothing, and be bored or depressed.
Please think about getting two and talk it over with your parents. Good luck with your new pet or pets if you get some

And let us know if you do