Congratulations on your children's recovery and enjoy every minute of your vacation.
Yes, you can ADD Rifampin to current antibiotic protocol. Our children have been on the same combination in the past along with IVIG for Selective Immune Deficiency. One thing you should be aware of regarding Rifampin........ you should not stop and restart for brief periods of time. So, if you start taking it...... take the entire 5 weeks you are away.