Students must first choose whether to use ¿Cuándo es tu cumpleaños? or ¿Cuándo es su cumpleaños? based on who they are asking. Then, they figure out their birthdays based on the clues given and write them in the "report." Finally, they figure out their ages. I have the students write them in complete sentences!
This is a fun way to familiarize students with question-asking. It also encourages their critical thinking skills. Plus it's fun!