Both of your kids are probably having flu like viral illness which can cause myalgia
. Give them bed rest
for body pain
and they will be fine in two or three more days. As already said, Amox is not going to help. Keep the m hydrating well. As long as they are not drowsy, drinking some fluids, passing urine same as before you need not worry.
Dr. Balaji Chinnasami MD
Assistant Professor, Pediatrics