I kept piggies as a child to early twenties
DD and I have kept piggies since she was 9yo (she's 16 now)
I love the bones of them but as you've now decided NOT to have them, I'll tell you the bad bits so you don't feel too bad.
Pulls up a chair:
The allergies - DD was fine with smooths and Abby (rossettes) but allergic to Rex (coarse) and very allergic to Teddy (coarse/fuzzy)
Teddy coat is GP6 , her adored boar she gets a rash when she handles him. The only option would be for her to give him to me , but she won't.
Hay is also an allergen
Hay gets bloody everywhere . Mine are indoors in Winter. Their hay creeps into the house all year but a constant battle in winter.
Guinea pigs don't smell. Hay does. They do pooh with abandon but mine are all pretty good at holding their pee. They have their ways of warning you, you just need to learn it , or you get peed on.
Some will dance, move their bottom backwards , our boar prattles on.
They are good little animals really .
They can be pricey with the hay and veg.
They are very noisy (especially indoors) and think nothing of telling you off if breakfast or dinner is late. If you open the fridge or chop. I couldn't eat a bag of crisps without being grassed up.
They denude the lawn like a swarm of locusts. Our lawn has a couple of huge rabbits runs on it for 6-8 months of the year .
They need a lot more space than you'd think. Ours have a playhouse that is adapted for them . Indoor winter they have the small bedroom and two big cages .
They don't really do much , eat, potter about , the odd popcorning. My NDN thought they were ugly and boring, I was 
at the ugly but compared to rabbits they're not athletic.
They need protected against everything. Heat,cold,draughts,foxes,cars,magpies. They cannot vomit so you need to know what they can/cannot eat.
They don't alwats get on. My GP7/GP8 can't be bonded with gP6 because GP8 attacks him.
They are famous for doing Well-To-Dead. When they're ill they hide it and its really hard to bring a guinea-pig back when they are ill.
So you get the Never Ending Spiral where you keep replacing them.
My guineas are all Rescues.
Look on Gumtree for the reasons people sell them. "Kids lost interest (obviously Adult Is Absolving Themselves of Parental Responsibilty" / Kids allergic / Moving / Lone pig as other one died/ Getting a puppy/ and my personal hate : Kids outgrown them they're living breathing animals not a pair of shoes 
Of course the positives of guinea-pigs outweigh the negitive. My 3 pigs are all 4yo now , so this is our last lot.
Once we get to one pig (hopefully not for a while) I'll keep that one indoors 24/7 , in the kitchen.
DD will be off to Uni in a couple of years and I;m getting too old to chase them in the rabbit run 
I think you need everyone on board , my DH isn't mad about the pigs , but if I'm not able to he'll feed and clean them (usually DD and I share it) and he'll buy them veg. It would be hard going if he wasn't on board . DD and I had proper flu this year, DH did over a week of pig care , bless him.