For an Outland application, it is strongly suggested that you complete the upfront medical, else you risk your entire application being returned as `incomplete'. Just follow the instructions that taffy7 has provided. Also, make sure that she uses an approved Panel physician (listed on CIC's website) and that the doctor uses the e-medical system to transmit the results to CIC electronically.
Regarding your second question; are you also sponsoring her son at this time, or is he being listed in her application as a non-accompanying dependant child? Even if he is not coming with her, he will need to have a medical exam too. If he is being sponsored (which it sounds like he is, since you're asking if he can leave his country), then she will absolutely need the father's written permission for the son to leave (unless he has forfeited his paternal rights).