Multiple answers can be obtained.
Glip's - Fill the 13 oz cup. Use the now-full 13 oz cup to fill the 5 oz cup. Put the remainder from the 13 oz cup into the 11 oz cup. Give 11 oz cup to child A to drink. Pour contents of 5 oz cup back into 13 oz cup. Refill 13 oz cup. Use 13 oz cup to fill 5 oz cup again. Give 13 oz cup to child B to drink, give 5 oz cup to child C. Refill child's C cup with the remaining 3 oz of medicine after child C drinks the first 5
Mine - Fill the 5 oz and 11 oz Containers from the 24 oz container. This leaves 8 oz in the 24 oz bottle. Next empty the 11 oz bottle by pouring the contents into the 13 oz bottle. Fill the 13 oz bottle from the 5 oz container (with 2 oz.) and put the remaining 3 oz in the 11 oz bottle. This leaves the 5 oz. container empty. Now pour 5 oz from the 13 oz bottle into the 5 oz bottle leaving 8 oz in the 13 oz bottle. Finally pour the 5 oz bottle contents into the 11 oz bottle giving 8 oz in this container.