Callie,
Here is something else for you to consider, since this is Ancients History, which my family is working through at the moment, the Bible readings are also history, and on days when there are other history readings from Pharaohs or Oxford there isn’t typically a Bible reading on that day. So, when we have had to skip days because of illness or appointments, we’ve been able to double up some readings without overloading the girls. For reference, my youngest is 10 years old. So, depending upon your children, you might be able to double up here and there, if you should want to go that route. Also remember that the 12th week is test week, so you can make up some of the readings at that time if you so choose.
Otherwise, you could do an extra 5 weeks of school time. Perhaps add an extra week and a half to each trimester. You would go a bit longer in your year that way, but you could always take a week or two break between the trimesters to help keep things light.
You could also choose to stop when you would normally and work through the last 5 weeks of the previous module before moving on to the next.
I’m not sure I was overly helpful to you, but perhaps someone more inspired will chime in as well.
Blessings on your endeavors,
~jacqleene