This probably isn't what you want to hear, but unless your parents are committed to the guinea pigs' best interest, it really isn't fair to get a pig at all. Guinea pigs need large cages and shouldn't be kept alone. They need fresh, high quality food which can get expensive, and their cages must be cleaned regularly. If your parents aren't willing to help meet these basic needs, how can you be sure that they will take your pigs to the vet if they need it? I recommend that you sit down with your parents, show them printed out pages from this forum, guinea lynx,
cavy spirit, etc. and discuss all aspects of guinea pig care. Be honest about the large time and financial committment. If your parents are just as enthusiastic about getting pigs as you are and can truly commit to their care for their whole lives (up to 8 years or so), then go for it. Otherwise, as badly as you want pigs, you should look into volunteering at a humane society or something similar. That way you would get to spend lots of time helping animals who need it without having to commit to their care long-term.