Thanks, petey_c for your insight.

So since there's no AC in the bedroom (it's central AC for the house) I will need a 20 amp (bathroom) and 15 amp(lights and receptacles) circuit for each bedroom. So the total for the two bedrooms will be 4 new circuits, if I understand you correctly. A 40 amp feed to a 100 amp subpanel box seems to be more than adequate.