I read that when binding from a DataSource, only one series can be accepted. So instead I created an updateDonut() function and perform a post to get the series data and then use setOptions() to assign the series. I have changed the returning JSON back to how it was in my first post. Here is the updated code:
donutChart = $(
series1 = result;
series2 = result;
It's now working exactly as I want it to.