I agree, pairs are best. I assume you built a Cubes and Cloroplast cage like these?
http://www.guineapigcages.com/ I always thought they looked so cool!
Almost all pet store cages are too small, with the exception of a few very large models (like the Marchiroro Tommy 120). Also, Guinea pigs need solid flooring, wire flooring can hurt their feet and the can catch and break legs in it.
No cedar, corn cob, or pine bedding. Cedar and Pine both have phenols which can cause upper respiratory issues in small animals. You know the scent they give off? Breathing it 24/7 isn't good for the little guys. I really like Carefresh Bedding which is recycled paper, but Aspen is an acceptable wood.
They do best in pairs. Males can be neutered, if you want an opposite sex pair. I like to neuter the males anyway. All of my boys marked with big puddles of urine- even when sitting on you. Neutering them eliminated the problem.
Make sure they are getting food rich in Vitamin C. They are the only animal other than humans that doesn't produce their own. If they don't get it, they can get scurvy and die. Commercial Guinea pig food ussually has it, but if the food is old, the Vitamin C breaks down. Some brand also don't seem to have enough. You can buy supplements, or be sure to feed fresh veggies with high C content.
Nail trimming is a must. Human nail clippers will work, or cat clippers. I've seen Guinea pigs with nails growing into their feet because the owners didn't realize they needed trimming.
Hay should be available 24/7. Use a grass hay like Timothy- Alfalfa is too high in calcium for daily feeding.
Make sure you have wooden chew sticks available all the time. Their teeth never stop growing, without something hard to chew on, they will grow so long that the poor pig cannot eat.
Also, they have guinea pig rescues if you are interested. Petfinder has 875 Guinea pigs listed for adoption right now-
http://www.petfinder.com/breeds/smallFurry
Remember that they can live 8 years with proper care. I would discuss this with your DD if you haven't already. They are a much longer term commitment than some other pocket pets.
The only other thing- they tend to be very shy and scared when they first come home. DD will probably want to hold them right away, but its best to leave them alone for a few days. I also seem to recall it works best to get one, give it a little time to tame down and get used to humans, then get a second. Two at a time are sometimes harder to tame. You should have a pair, but taming wise it works best to have one tame before adding a second.
