Me and 3 year old son just caught the stomach flu, what can I do to make this go away faster, and keep it from spreading?

Good hygiene . Stomach "flu" is most commonly caused by a virus. Viruses are spread by saliva and respiratory droplets. Good handwashing, and not sharing germs are the keys to prevention of the virus. Unfortunately there is no cure. Treatment is supportive with nausea meds and fluids as tolerated. Be careful to watch for dehydration and always best to see your doc to make sure it's nothing more.
Fluids, Brat diet. The stomach flu usually will take 5-7 days to get better. Make sure you and your son are well hydrated. Avoid fatty foods and juices with lot of sugar. We usually recommend brat (bananas, apples, rice, toast) diet which will help the stomach to settle down and be less irritated. You also need to practice hygiene measures like washing hands thoroughly with soap and water after every toilet use.
Hand washing. . Hygiene is key to stop spread of germs. Specially stomach infections. You can take probiotics to try to help the infection get better sooner and sometimes even prevent it, to some extent.
Hygiene & diet. Wash your hands. Wash his hands. Use the "sani cycle" on automatic dishwasher if you have one. Resume regular diet as soon as tolerated but eat/drink small amounts often. Use good food practices: hot foods hot, cold foods cold, watch for contamination in food prep, trash leftovers > 3 days, check refrigerator temperature.