My 2 Year Old Is Sick?

Hi my 2 year old daughter has had a Fever and Vomiting since Wednesday. The fever goes down and comes back. She doesn't want to eat anything but she drinks alot, and she's been vomiting everytime we put her down for a nap. Also now my son just started vomiting. Do you know what this is. Could it be just the Stomache Flu or do you think it is something worse? Should I go to the doctor and get them checked?