I would highly recommend getting your pig to a vet as soon as possible. These little guys don't have much reserve, and being prey animals, they tend to not show they are sick until they are very sick. That being said, in the meantime I would try to see if she is able to swallow. If so, I would use a syringe or dropper to give her water and/or mix in some gatorade. This will help keep her hydrated, and the gatorade has some electrolytes. Oxbow makes a product called critical care, which is a powder you add water to and can syringe feed. Make sure your pig is at a comfortable temperature, and keep her clean and dry if she is unable/unwilling to move after going to the bathroom. I am not sure what is causing your pig's signs, she could have a bacterial infection, she could be weak from lack of vitamin C, she could be blocked (constipated) or have tooth issues that have caused her to not eat as much and she could have a low blood sugar, etc. The only way to find out what is causing the problem and fix it is to have her examined by a vet. Hopefully with the at home care I told you about, you will be able to get her through until you can get her seen.

I am very sorry to hear that.

I am not sure how young your son is, but it can be very difficult to explain death to children. I guess my advice would be to explain that the guinea pig is no longer suffering. I am not sure if you are religious or not, but there is a poem written about pet loss called the rainbow bridge. http://www.petloss.com/rainbowbridge.htm You may find this helpful, you may not. Let your son know it is okay to grieve the pet, as it was an important part of his life, and make sure he understands that this was not his fault. I'll be thinking of you during this difficult time.