A couple of points -
Even at the lower figure of 5 amps (at 12v), 2 of them over 8 hours is going to use 80 amp hours. That is beyond the one day capacity of most single 12V house batteries without recharging. I have no idea of what the amp hour capacity of your 400 Powerpak is, but if it is portable, I doubt it is near even the smallest standard 12V battery.
If your solar
panels produce 20 watts (each?) for a total of 40 watts, over a typical day you can expect to produce no more than 20 amp hours; probably less.
The combination is not going to work. In my case I use around 20 - 25 amp hours per day. I have a pair of 6V batteries with a capacity of 232 amp hours. In the summer with a roof mounted 95 watt panel I barely keep up. In the winter (low sun angle) or shade, it takes the combination of the roof panel plus a 160 watt folding panel to keep up with the normal usage.
You are going to need both more battery capacity & more solar panel(s) to put together a system that can produce enough energy to run the CPAP machines for any reasonable length of time.
One possibility - if you can run the machines without the humidifiers, it will save a considerable amount of power.