I'm adopting a pair of guinea pigs for my daughter for xmas. They are 4 months old and male. The girl we are adopting them from said she gives them pellets and as a snack kale, cucumbers, carrots and celery. We are brand new to guinea pigs but I already bought timothy hay and the pellets but not sure how to work in the people food. We are getting them this friday and I didn't know if I needed to slowly introduce other types of food? Any suggestions would be great. Thanks